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Parasites of the African painted dog (Lycaon pictus) in
captive and wild populations: Implications for conservation
Amanda-Lee Ash
Bachelor of Animal and Veterinary Biosciences (Hons)
La Trobe University, Victoria
Faculty of Health Sciences
School of Veterinary and Biomedical Sciences
Murdoch University
Western Australia
This thesis is presented for the degree of Doctor of Philosophy of Murdoch University 2011
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I declare that this thesis is my own account of my research and contains as its main
content work which has not previously been submitted for a degree at any other tertiary
educational institution.
……………………………..
Amanda-Lee Ash
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Abstract
The African painted dog (Lycaon pictus) is a highly endangered carnivore of sub-
Saharan Africa, which in the last century has suffered a population decline of almost
99%. With only 3,000-5,500 animals remaining in the wild it is imperative to
understand all threatening processes to which these animals may be exposed. The
impact that parasites and other infectious agents have on wildlife has been increasingly
recognized within conservation programs. Stressors such as human encroachment and
habitat destruction are altering the incidence and effect that these pathogens have on
wildlife populations, especially those endangered and under stress.
A parasitological study was conducted on captive and wild populations of the African
painted dog over a three year period. Collaborations with three captive animal facilities
and three in situ conservation groups within Africa allowed for a broad sample base
from which variation in parasite prevalence and diversity could be identified. A
combination of traditional microscopy techniques and molecular characterisation of
parasite species were employed to obtain comprehensive data on the prevalence and
diversity of gastrointestinal parasites observed in faecal samples collected from painted
dogs.
Parasite prevalence within wild populations was 99% with a similar parasite
community composition observed among all three wild populations. Five of the seven
parasite genera observed in this study have not been reported before in this host.
Additionally, molecular characterisations identified the potentially zoonotic species
Giardia duodenalis, Ancylostoma braziliense and an ambiguous species of taeniid, all
of which have also not been previously reported in this host.
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The prevalence of parasites within captive populations was 15% with Giardia
duodenalis being the dominant of the only two parasite species observed. The overall
lack of prevalence and diversity of parasites observed in captive populations could be
of significance for facilities involved in reintroduction programs. Particularly as
immunologically naïve captive animals may be unable to cope with exposure to a
‘natural’ parasite load in the wild environment, leading to an ultimate decrease in
reintroduction success.
Gastrointestinal parasites detected in faecal samples from wild and captive populations
of the African painted dog during this study
Wild Captive
Parasite Taxon
observed
Taeniid Giardia
Ancylostoma Spirometra
Spirometra
Giardia
Coccidia
Sarcocystis
Filaroides
This study has obtained detailed baseline data of parasitism within populations of the
African painted dog in captive and wild environments. The large proportion of new
discoveries in this study demonstrates the paucity of information currently available on
parasitism within this host species. It is hoped this information will assist in
conservation efforts by a) recognising the challenges of parasite control in captive
populations, particularly those involved in reintroduction and/or translocation
programs, and b) being able to identify deviations from baseline parasite levels in wild
populations which could be indications for emerging exotic and/or zoonotic disease.
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Publications
Refereed journal articles:
Ash, A., Lymbery, A., Lemon, J., Vitali, S., Thompson, R.C.A. (2010). Molecular
epidemiology of Giardia duodenalis in an endangered carnivore – the African painted
dog. Veterinary Parasitology, 174, 206-212.
Conferences
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2010). Significance of parasitism
in an endangered carnivore - the African painted dog. Conference Proceedings: XX11
International Congress of Parasitology, Melbourne, Australia. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Vitali, S., Thompson, R.C.A. (2009). Giardia
duodenalis isolates from captive and wild populations of the African painted dog
(Lycaon pictus). Conference Proceedings: ASP & ARC/NHMRC Research Network
for Parasitology Annual Conference. Sydney, Australia, pp 54. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2009). Parasites of the African
Painted dog (Lycaon pictus) in wild and captive populations: potential conservation
impacts. Conference Proceedings: 22nd Conference of the World Association for the
Advancement of Veterinary Parasitology (WAAVP), Calgary Canada, pp 86.
(Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2008) Parasites of the African
painted dog (Lycaon pictus) in wild and captive populations: potential conservation
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impacts. Conference Proceedings: 21st Australasian Wildlife Management Society
Conference. Fremantle, Australia, pp 44. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2007). Parasites of the African
painted dog (Lycaon pictus) in wild and captive populations: potential conservation
impacts. Conference Proceedings: ASP & ARC/NHMRC Research Network for
Parasitology Annual Conference. Canberra, Australia, pp 95. (Abstract)
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Acknowledgements
I would firstly like to thank my three supervisors, Andy Thompson, Alan Lymbery and
John Lemon for their invaluable guidance throughout this project.
Secondly, the fabulous field assistance given by the staff of the Zambian Carnivore
Project (Matt Becker, Egil Droge and Claire Harrision) and the Wild Dog Project
(Robin Lines and Anna) for making my forays into deepest Africa a little less daunting.
I now have the ability to navigate rough muddy roads in various 4WD vehicles and deal
with angry elephants, hungry hyaena, thieving baboons and the ever present lion all in
the quest for African painted dog poo. Additionally the staff at DeWildt wildlife trust
(Alan and Gabby) for assistance and protection in roaming occupied enclosures for
samples, whilst also chasing cheetah out of trees. And of course the keepers and vets at
Perth and Monarto zoo.
Thirdly, the assistance I was given in the lab was lifesaving. I was fortunate in having
access to expertise from various people including Cath Covacin, Aileen Elliot, Russ
Hobbs and Louise Pallant, all of which made my task that much easier. Additionally,
the post-grad office crowd were always available for a little light comic relief.
And finally, to all my family and friends who tried not to think I was completely mad
for taking on a doctorate and for R who was a calming influence during the rough and
rocky patches of field work, lab work and write up.
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Table of Contents
Abstract ............................................................................................................................... iii
Publications .......................................................................................................................... v
Conferences .......................................................................................................................... v
Acknowledgements ............................................................................................................ vii
Table of Contents ............................................................................................................. viii
List of Tables ..................................................................................................................... xiv
List of Figures ................................................................................................................. xviii
Chapter 1 Introduction ................................................................................... 1
1.1 Parasites in wildlife ........................................................................................................ 2
1.2 Importance of parasites in conservation ...................................................................... 2
1.2.1 Direct impacts ..................................................................................................................4
1.2.2 Indirect impacts ................................................................................................................8
1.2.3 Co-extinction events/biodiversity considerations .......................................................... 11
1.2.4 Assessing effects of human influences .......................................................................... 12
1.3 The host, the African painted dog (Lycaon pictus).................................................... 14
1.3.1 Ecology of the African painted dog ............................................................................... 15
1.3.2 Conservation issues for the African painted dog ........................................................... 16
1.4 Parasites and the African painted dog ....................................................................... 17
1.4.1 Host ecology and parasites ............................................................................................. 17
1.4.2 Parasites recorded from the African painted dog ........................................................... 18
1.4.3 Gaps in current knowledge of parasitism in the African painted dog ............................ 20
1.5 Management of wild species ........................................................................................ 21
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1.5.1 Captive environments .................................................................................................... 21
1.5.2 Reintroduction programs ............................................................................................... 23
1.5.3 Translocation programs ................................................................................................. 23
1.6 Goals for this study ...................................................................................................... 24
Chapter 2 General materials and methods ................................................. 27
2.1. Study design ................................................................................................................. 28
2.2 Captive populations ..................................................................................................... 29
2.2.2 Perth Zoo ........................................................................................................................ 29
2.2.3 Monarto Zoo .................................................................................................................. 31
2.2.3 DeWildt Wildlife Trust .................................................................................................. 32
2.3 Wild populations .......................................................................................................... 33
2.3.1 South Luangwa National Park – Zambia ....................................................................... 33
2.3.2 Nyae Nyae Conservancy – Namibia .............................................................................. 35
2.3.3 Hwange National Park – Zimbabwe .............................................................................. 36
2.4 Sampling methodology ................................................................................................ 37
2.4.1 Ethics and permits .......................................................................................................... 38
2.4.2 Locating packs ............................................................................................................... 39
2.4.3 Sample collection ........................................................................................................... 40
2.4.4 Sample movement .......................................................................................................... 41
2.5 Parasitological techniques ........................................................................................... 42
2.5.1 Microscopy; qualitative analysis .................................................................................... 42
2.5.2 Microscopy; quantitative analysis .................................................................................. 44
2.5.3 Molecular characterisation ............................................................................................. 45
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Chapter 3 Diversity and prevalence of gastrointestinal parasite fauna
within captive and wild populations of the African painted dog .............. 46
3.1 Introduction .................................................................................................................. 47
3.2 Materials and methods ................................................................................................ 49
3.2.1 Sampling protocol .......................................................................................................... 49
3.2.2 Parasite identification and quantification ....................................................................... 51
3.2.3 Host and environmental variables .................................................................................. 52
3.2.4 Data analysis .................................................................................................................. 52
3.2.4.1 Descriptors used ..................................................................................................... 52
3.2.4.2 Levels of testing ....................................................................................................... 53
3.2.4.3 Statistical analysis .................................................................................................. 55
3.3 Results ........................................................................................................................... 56
3.3.1 Variation between captive and wild populations ........................................................... 56
3.3.2 Variation between packs ................................................................................................ 58
3.3.3 Variation among different geographic locations ............................................................ 60
3.3.4 Variation between different seasons .............................................................................. 62
3.3.5 Variation between host age and sex ............................................................................... 64
3.3.6 Parasite aggregation within hosts ................................................................................... 64
3.4. Discussion..................................................................................................................... 65
3.4.1 Parasite diversity ............................................................................................................ 65
3.4.2 Influence of geographic, seasonal and demographic factors ......................................... 68
3.4.3 Parasites of wild and captive populations ...................................................................... 70
3.4.4 Conclusions .................................................................................................................... 71
Chapter 4 Molecular epidemiology of Giardia duodenalis in an
endangered carnivore – the African painted dog ....................................... 72
4.1 Introduction .................................................................................................................. 73
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4.2 Materials and methods ................................................................................................ 75
4.2.1 Sample collection ........................................................................................................... 75
4.2.2 Parasitological techniques .............................................................................................. 75
4.2.3 DNA extraction .............................................................................................................. 76
4.2.4 Amplification of 18S rRNA locus ................................................................................. 76
4.2.5 Amplification of β-giardin locus .................................................................................... 77
4.2.6 Amplification of the glutamate dehydrogenase locus .................................................... 78
4.2.7 Data analysis .................................................................................................................. 79
4.3. Results .......................................................................................................................... 80
4.3.1 Prevalence of infection .................................................................................................. 80
4.3.2 Molecular characterization of Giardia duodenalis isolates ........................................... 81
4.4. Discussion..................................................................................................................... 84
4.4.1 Conclusions .................................................................................................................... 89
Chapter 5 Hookworm species of the African painted dog and the
significance of infection ................................................................................. 90
5.1 Introduction .................................................................................................................. 91
5.1.1 Hookworm in the canid host .......................................................................................... 92
5.1.2 The zoonotic potential of canid hookworm species ....................................................... 93
5.1.3 Hookworm in the African painted dog and other carnivores in Africa .......................... 94
5.1.4 Diagnosing hookworm infections .................................................................................. 95
5.2 Materials and methods ................................................................................................ 96
5.2.1 Sample collection ........................................................................................................... 96
5.2.2 Parasitological techniques .............................................................................................. 96
5.2.3 DNA extraction .............................................................................................................. 97
5.2.4 Amplification of Ancylostoma spp. isolates at the ITS1 and ITS2 regions .................... 97
5.2.5 Data analysis .................................................................................................................. 98
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5.3 Results ........................................................................................................................... 98
5.3.1 Prevalence of infection .................................................................................................. 98
5.3.2 Molecular characterisation of Ancylostoma spp. isolates ............................................ 100
5.4 Discussion.................................................................................................................... 101
5.4.1 Conclusions .................................................................................................................. 106
Chapter 6 Detecting Taenia species of the African painted dog ............. 108
6.1 Introduction ................................................................................................................ 109
6.2 Materials and methods .............................................................................................. 114
6.2.1 Sample collection ......................................................................................................... 114
6.2.2 Parasitological techniques ............................................................................................ 115
6.2.3 Identification of proglottids ......................................................................................... 115
6.2.4 DNA extraction ............................................................................................................ 116
6.2.5 Amplification of Taeniid isolates at the 12S rRNA locus ........................................... 116
6.2.6 Data analysis ................................................................................................................ 117
6.3 Results ......................................................................................................................... 118
6.3.1 Prevalence of Infection ................................................................................................ 118
6.3.2 Identification of taeniid spp. proglottids ...................................................................... 120
6.3.3 Molecular characterisation of taeniid sp. isolates ........................................................ 121
6.3.4 Phylogenetic analysis of Taenia spp. isolates .............................................................. 124
6.4 Discussion.................................................................................................................... 125
6.4.1 Conclusions .................................................................................................................. 129
Chapter 7 General discussion ..................................................................... 130
7.1 Conservation status of the African painted dog ...................................................... 131
7.2 Increasing importance of studies of parasites ......................................................... 131
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7.3 Parasitological techniques ......................................................................................... 132
7.4 Implications for biodiversity conservation .............................................................. 133
7.5 Parasitism in natural populations ............................................................................ 134
7.5.1 Baseline data ................................................................................................................ 134
7.5.2 Parasite threats to painted dogs .................................................................................... 135
7.5.3 Zoonoses/anthropozoonoses ........................................................................................ 136
7.6 Parasitism in captive populations ............................................................................. 137
7.7 Project limitations and future research ................................................................... 138
7.7.1 Sample collection and analysis .................................................................................... 138
7.7.2 Continued surveillance ................................................................................................. 139
7.7.3 Threat of emerging disease .......................................................................................... 140
7.7.4 Captive management .................................................................................................... 140
Appendix 1. Taenia spp. proglottid key. From Verster (1969) .................................. 142
References ......................................................................................................................... 143
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List of Tables
Table 1.1 An overview of the major factors of the host/parasite relationship.
Positive effects are those that are assumed to be beneficial to an
individual or population of hosts; negative effects are assumed to be
harmful to an individual or population of
hosts………………………………………………………..……………4
Table 1.2 A brief natural history of parasites observed in the African painted dog…………………………………………………………………19-20
Table 3.1 Number of faecal samples obtained from all captive and wild
populations during the study period….……………………………….50
Table 3.2 A hierarchical list of comparisons made between host groups with
descriptions of the data used at each level……………………….….…54
Table 3.3 The prevalence (with 95% confidence intervals in parentheses) and
diversity of GI parasites detected in faecal samples from all captive and
wild populations of the African painted dog……………………..……57
Table 3.4 Prevalence (with 95% confidence intervals in parentheses) of GI
parasites detected in faecal samples from two packs within the Zambian
study population………………………………………………….…….58
Table 3.5 The overall prevalence (with 95% confidence intervals in parentheses)
and diversity of GI parasites detected in faecal samples from three wild
populations - Zambia, Zimbabwe and Namibia…………………..…...61
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Table 3.6 Prevalence of the main GI parasites (with 95% confidence intervals in
parentheses) detected in faecal samples from all wild populations in wet
and dry
seasons………………………………………………………………....62
Table 3.7 Aggregation of parasite species within host populations in Zambia,
Namibia and Zimbabwe using the Index of Discrepancy values (D).…65
Table 3.8 GI parasite genera observed in this study and in the published
literature………………………………………………………………..65
Table 4.1 Prevalence of Giardia duodenalis (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild
populations of the African painted dog……………………..…………80
Table 4.2 Genotypic characterisation of Giardia duodenalis isolates from
individual African painted dogs at the18S rRNA, β -giardin and gdh
loci. * Wild animals over 2yrs of age were allocated as Adult……...…82
Table 4.3 Prevalence (with 95% confidence intervals in parentheses) and
genotypic characterisation of Giardia isolates obtained in a captive
population of African painted dogs over a three year period………….83
Table 4.4 Assemblages of Giardia duodenalis observed in both wild canids and
domestic dogs noted in the literature and this study. Number of times
reported in literature is presented as (r=)…………………………….86
Table 5.1 Prevalence of Ancylostoma spp. (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild
populations of the African painted dog………………………………99
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Table 5.2 Prevalence of Ancylostoma spp. observed in the Zambian and Namibian
populations of the African painted dog over a three year period. Sample
size (n) and 95% confidence intervals in parentheses……….…….....99
Table 5.3 Genotypic characterisation of Ancylostoma spp. isolates obtained from
wild populations of the African painted dog within Zambia and
Namibia. Percentages for matched identities with published sequences in
parentheses…………………………………………...……………….100
Table 5.4 Summary of the nucleotide variations detected between the painted dog
isolate from Zambia (Z-Ka01) and reference sequences for A. caninum
and A. duodenale. Alignment was conducted in Sequencher™ 4.8 and
dots indicate identity with the first sequence…………...…………….101
Table 6.1 Definitive and intermediate hosts of Taenia spp. infecting African
carnivores………………………………………………...…………...112
Table 6.2 Prevalence of taeniids (with 95% confidence intervals in parentheses)
detected in faecal samples from wild populations of the African painted
dog………………………………………………………..…………..119
Table 6.3 Prevalence of taeniids observed in the Zambian and Namibian
populations of the African painted dog over a three year period. Sample
size (n) and 95% confidence intervals in parentheses……..…………119
Table 6.4 Species identification of taeniid proglottids obtained from painted dog
populations……………………………………………...…………….120
Table 6.5 Genotypic characterisation of taeniid spp. species isolates obtained from
wild populations of the African painted dog within Zambia, Namibia
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and Zimbabwe. Percentages for matched identities with published
sequences on GenBank in parentheses……………………………….122
Table 6.6 Summary of the nucleotide variations detected between taeniid isolates
from Zambian and Namibian populations of the African painted dog and
reference sequences for T. multiceps and T. serialis (GenBank accession
numbers GQ228818, DQ408418 and EU219546, DQ104238).
Alignment was conducted in Sequencher™ 4.8 and dots indicate identity
with the first
sequence……………………………………..………………………..123
Table 6.7 Pairwise comparison of sequence variation (%) within the 12S rRNA
loci of T. multiceps and T. serialis reference sequences and taeniid
isolates obtained from Namibian and Zambian populations of the
African painted
dog…………………………………..………………………………..124
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List of Figures
Figure 2.1 Location of painted dog study sites within Australia………………....29
Figure 2.2 Painted dog exhibit at Perth Zoo showing the water feature and animals
resting in the shade……………………………………………………30
Figure 2.3 Painted dog exhibit at Monarto zoo showing the animals in the large
fenced
enclosure……………………………………………………………....31
Figure 2.4 Painted dog enclosure at DeWildt Wildlife Trust showing grassy and
shady environment……………………………………………………32
Figure 2.5 Locations of the painted dog study populations within Africa……….33
Figure 2.6 South Luangwa National Park, Zambia. Open grassland area with acacia
and mopane woodland in the background, which is typical of the habitat
frequented by painted dog populations……………………………….34
Figure 2.7 Nyae Nyae Conservancy, Namibia. One of the few sandy roads
available to use, surrounded by thick grass and acacia trees………….35
Figure 2.8 Game managed area of Hwange National Park, Zimbabwe. Open area
with miombo woodland and acacia in the background, typical for
painted dog
habitat………………………………………………………………...37
Figure 2.9 The left and right side views of an individual painted dog from the
Katete pack in Zambia. ID number P3 0308………………………….40
Figure 2.10 Parasite ova of taeniid spp. and Giardia spp. cysts observed during
microscopy analysis of painted dog faecal samples. Morphology and
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size are substantially different between the two genera, allowing for
unambiguous identification……………………………………………43
Figure 3.1 Parasite load (N), species richness (S) and species evenness (H) in
captive and wild populations of the African painted dog……………..56
Figure 3.2 Parasite load (N), species richness (S) and species evenness (H) in two
packs within the Zambian study population…………………………..59
Figure 3.3 A multidimensional scaling plot of data from two African painted dog
packs within the Zambian population based on Bray-Curtis similarity
coefficients of parasite infracommunity composition…………………59
Figure 3.4 Parasite load (N), species richness (S) and species evenness (H) in three
wild populations of the African painted dog…………………………60
Figure 3.5 Parasite load (N), species richness (S) and species evenness (H) between
wet and dry seasons in all wild populations of the painted dog………63
Figure 3.6 A multidimensional scaling plot of data from wet and dry environments
of three wild populations based on Bray-Curtis similarity coefficients of
parasite infracommunity……………………………………………….63
Figure 5.1 Depiction of the lifecycle of Ancylostoma caninum in domestic dogs
adapted from www.Apaws.org...............................................................92
Figure 6.1. The lifecycle of a taeniid species depicting the transmission cycle
between predator (definitive host) and prey (intermediate host)……111
Figure 6.2 A depiction of the genital atrium of T. crocutae as an example of the
morphological features used in identification of proglottids. From
Verster (1969). Appendix 1 displays the proglottid key used for
identifying samples obtained in this study……………………………116
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Figure 6.3 Multiplex PCR of taeniid isolates from wild painted dog populations at
the 12S rRNA locus. Lanes 2-11 are painted dog samples from Zambia
and Namibia. Lane 13 is the negative control; 14-16 are the positive
controls for Taenia sp, E. granulosis and E. multilocularis…………121
Figure 6.4 Phylogenetic relationships, inferred using the Neighbour-joining method
between taeniid isolates from African painted dogs and reference
isolates of T. multiceps and T. serialis based on sequence data of the 12S
rRNA locus. Representatives of Taenia sp. used for comparison are
labelled with accession numbers as published on GenBank, with E.
granulosus as the out-group. Numbers at nodes refer to bootstrap values
(1500 replicates) > 20%.
………………………………………………………………………125
Chapter 1 - Introduction
1
Chapter 1
Introduction
Chapter 1 - Introduction
2
1.1 Parasites in wildlife
Comprehensive research on parasitism within wildlife populations has, to date, been
minimal (De Leo and Dobson, 2002; Altizer et al., 2003a; Morand et al., 2006). Of these
studies most have been focused on the threat disease may pose to livestock or human
populations, rather than gaining insight into the biodiversity and role these host/parasite
interactions have within the ecosystem (Hudson et al., 2006; Thompson et al., 2010).
Parasitism is the commonest life style on earth (Poulin and Morand, 2000) and parasites
are therefore a major component of ecosystems. An increasing number of studies are
showing that parasites are important in maintaining ecosystem function through their effect
on regulating host population sizes, mediating predatory and competitive interactions
among free living organisms and acting as ecosystem engineers (Anderson, 1972; Temple,
1987; Jones et al., 1994; Hudson et al., 1998). Therefore, understanding parasitism within
wild populations should be an integral part of any wildlife monitoring program and a key
component of wildlife conservation efforts.
1.2 Importance of parasites in conservation
As wildlife populations continue to decline, the need for active conservation of many
species becomes vital. For this to be successful it is essential that there is a thorough
understanding of all threatening processes within the wild environment (Peterson, 1991).
Until recently, there has been a very one dimensional view of the role played by parasites
in wildlife conservation programs. Parasite infection has usually been considered simply as
another threatening process which may require intervention (Daszak et al., 2000; Applebee
et al., 2005; Deredec and Courchamp, 2006; Penzhorn, 2006; Thompson et al., 2010). The
Chapter 1 - Introduction
3
reality however, is much more complex. An early study by Sachs and Sachs (1968), for
example, noted that wild animals were often heavily parasitised, when compared with
domestic animals, but showed apparent health. This display of health may be the result of
acquired immunity by the host or, as has been previously noted, wild animals tend to
manifest few recognizable signs of disease (Sachs and Sachs, 1968; Young, 1969). For
example, wild populations of zebra are known to harbour a variety of Cyathostomum spp.,
of which several species are pathogenic to domestic equines, but the zebra host appears to
display no clinical effects (Roberts et al., 2002). Sachs and Sachs (1968) qualified that this
display of health should not be confused with non-pathogenicity of parasites in wild
animals but rather a favourable balance between the host and its parasite community
established through a long evolutionary process. This evolutionary process has often been
referred to as an ‘arms race’ in reference to the constant battle between host and parasite to
gain the upper hand (Dawkins and Krebs, 1979). The outcomes of this are complex
host/parasite relationships which can be stable, cyclical or chaotic with equally complex
effects (May and Anderson, 1983). The complexity of the co-evolutionary relationship
between host and parasites means that parasitism can have both positive and negative
effects for individual hosts, for host populations and for communities of free living
organisms (Table 1.1). These effects arise because of both the direct impact of parasites in
causing disease and indirect impacts of parasites in mediating competitive and predatory
interactions among free-living organisms.
Chapter 1 - Introduction
4
Table 1.1 An overview of the major factors of the host/parasite relationship. Positive
effects are those that are assumed to be beneficial to an individual or population of hosts;
negative effects are assumed to be harmful to an individual or population of hosts.
Factor Effects at individual level Effects at population/community level
Positive Negative Positive Negative
Direct impacts of parasitism
Clinical &
Sub-clinical
disease
Development of
host immune
system
Morbidity and
death of susceptible
individuals
Avoiding
overpopulation
Maintenance of
genetic diversity
Local extinction
Regulating host
population size
Development of
host immune
system
Reduced fecundity
and survival of host
Increased host
population size
Decreased host
population size
Indirect impacts of parasitism
Interspecific
competition
Increased
competitive success
Decreased
competitive success
Increased resources
for successful
competitor species
Local extinction of
unsuccessful
competitor species
Manipulation of
prey behaviour
Increased prey
capture
Increased predation
rate
Increased
population size of
predator species
Reduced population
size of prey species
1.2.1 Direct impacts
The direct impacts of clinical disease from parasitism on the host are largely negative at
both the individual and population level as a significant parasite burden can lead to severe
morbidity or death. For example, at the individual level a heavy infection of hookworm in
young or immunocompromised animals can lead to severe anaemia and death of those
individuals (Bowman et al., 2003). At the population level gastro intestinal (GI) parasites
Chapter 1 - Introduction
5
such as Trichostrongylus sp. are capable of inducing large population crashes in wild and
domestic species. Hudson et al. (1992) observed this in wild populations of red grouse,
whilst livestock farmers have had long standing battles to reduce heavy stock losses due to
strongyle infections (Herlich, 1978; Fabiyi, 1987). Less obvious are the effects of
subclinical disease on the host however, there is growing evidence to suggest the effects
can be severe. One example is the protozoan parasite Giardia spp. Infection with this
parasite is often asymptomatic but studies have shown that long term infections can lead to
growth retardation in the host, particularly when suffering from poor nutrition (Astiazaran-
Garcia et al., 2000; Berkman et al., 2002). Whilst studies on Giardia spp. have been
focused on human infections this parasite is becoming increasingly recognised in wildlife
populations and therefore may be of similar significance, especially to endangered
populations with declining food resources. Evidence for this has been seen in a study on
red colobus monkey (Piliocolobus tephrosceles) populations living in fragmented forests
of Uganda (Chapman et al., 2006). This study found that populations of red colobus
monkeys, which were experiencing a decline in food availability, were at greater risk of the
detrimental effects of gastrointestinal parasites.
To further complicate matters, wild hosts are often infected with more than one parasite
(polyparasitism) which can sometimes alter or amplify the effects of any subclinical
disease. A recent example of this was illustrated in a study by Munson et al. (2008) who
conducted an analysis of historical data of canine distemper virus (CDV) epidemics within
populations of the African lion. They discovered that these epidemics coincided with
unusually high levels of the blood parasite Babesia, which were in turn the result of high
exposure to the tick vector after periods of drought. Babesia infections in wild hosts are
Chapter 1 - Introduction
6
often stable but this study suggests that the subclinical effects of this parasitic infection can
leave the host susceptible to other pathogens (Penzhorn, 2006; Munson et al., 2008). These
complex interactions make the ability to detect the causative agent of disease within hosts
harbouring multiple parasites extremely difficult. Compiling comprehensive baseline data
and conducting continual surveillance on the parasite fauna within different wild host
populations may increase the chances of detecting and predicting these pathogenic
outbreaks.
Consequences of clinical and subclinical disease may include the regulation of host
populations. Mathematical modelling has shown that parasites can provide density
dependent regulation of their host populations through effects on both host mortality rates
and host fecundity rates (May and Anderson, 1978; McCallum and Dobson, 1995). This
has been successfully demonstrated in laboratory studies of helminth infections in snails,
fish and mice (Scott and Anderson, 1984; Anderson and Crombie, 1985; Scott, 1988). For
example, the nematode Heligomosomiides polygyrus introduced into mice populations
resulted in dramatically reduced host densities, which subsequently increased on removal
of the nematode (Scott, 1987). This has also been demonstrated in a wild population of red
grouse (Lagopus lagopus scotius) and the nematode Trichostrongylus tenuis (Hudson et
al., 1992; 1998). Experimental removal of this parasite from populations of red grouse led
to greater clutches, higher hatching success and chick survival, however the control
population continued to display reduced fecundity and cyclical population crashes.
A lesser known aspect of parasitism is the beneficial effects which may be gained by the
host. As a result of the evolutionary arms race between host and parasite it has been
Chapter 1 - Introduction
7
proposed that parasites actively promote host immune systems and drive genetic diversity,
and consequently act as a buffer against disease (Windsor, 1998; Altizer et al., 2003a;
2003b; Lindstrom et al., 2004; Maillard and Gonzalez, 2006). Early exposure to parasites
can allow the host to build up effective immunity to withstand later heavy challenges. For
example, Carroll and Grove (1985) demonstrated that dogs currently infected with small
numbers of hookworms developed a functional protective immunity when challenged with
a large inoculum of infective hookworm larvae, whereas dogs previously uninfected with
hookworm developed marked anaemia when challenged with the same large inoculum. A
similar benefit observed is con-concomitant immunity which is the ability of the host to
mount an effective defence against parasite larval stages whilst being unable to clear a
burden of adult worms (Smithers and Terry, 1969). This can create an immunological
barrier against continual infection and restrict burden size within the host. The most
common examples of this are the schistosomes whereby immunologically invisible adult
worms established within the host are responsible for generating an anti larval immune
response which prevents any subsequent infection (Smithers and Terry, 1969).
Another perspective is the well documented theory of the ‘hygiene hypotheses’ (Cookson
and Moffatt, 1997; Yazdanbakhsh et al., 2002; Cooke et al., 2004). This has been referred
to principally within human hosts and proposes that completely eradicating and/or limiting
exposure of parasites from the host in a short evolutionary time span can lead to a
disruption in the host immune system resulting in autoimmune diseases such as ulcerative
colitis, asthma and other allergies (Yazdanbakhsh et al., 2001; Lakatos et al., 2004; Whary
and Fox, 2004). Evidence for this was documented in a human trial with long-term
Crohn’s disease patients who were seen to have a marked decrease in symptoms when
Chapter 1 - Introduction
8
infected with a nematode known to be non-pathogenic to humans Trichuris suis (Summers
et al., 2005). This study proposed that the introduction of a parasite into the host reinstated
normal functionality of the immune system.
Host genetic diversity is known to play an important role in enabling natural populations to
withstand widespread epidemics and is especially important in declining populations
(Frankham, 2005). Parasites represent powerful selective agents in natural populations and
are consequently a driving force behind species and genetic diversity (Altizer et al.,
2003b). This was demonstrated in a study of wild populations of Soay sheep (Ovis aries)
infected with intestinal nematodes (Paterson et al., 1998). Allelic variation within the
major histocompatibility complex (MHC) of Soay sheep was significantly associated with
juvenile survival and parasite resistance and it was concluded that parasites played a large
role in maintaining genetic diversity within this host population.
1.2.2 Indirect impacts
The indirect impacts of parasitism are comparatively less well understood than are the
direct effects, but studies are demonstrating the significance these interactions have within
ecosystems (Loreau et al., 2005). Parasites have been observed to be capable of mediating
interspecific competition between host populations and manipulating predator/prey
dynamics (Anderson, 1972; May and Anderson, 1978; Hudson et al., 1992; McCallum and
Dobson, 1995; Hudson et al., 1998; Jog et al., 2005; Barnes et al., 2007).
Chapter 1 - Introduction
9
Interspecific competition mediated by parasites has the potential to influence the structure
of ecological communities, the viability of each species within a community and the
potential for new species to invade a community (Thomas et al., 2005). An example of
parasite mediated competition has been observed in populations of white tailed deer
(Odacoileus virginiatus) infected with the parasite Parelaphostrongylus tenuis. White
tailed deer show minimal effects to an infection with this parasite but other cervids suffer
severe neurological effects and death (Anderson, 1972). This prevents invasion by exotic
cervids, leaving the white tailed deer with substantially less competition for food resources
in the area (Anderson, 1972). The inability to introduce domestic cattle into tsetse fly
zones of Africa is another example of parasite mediated competition. Tsetse flies are the
vector for Trypanosoma brucei and T. congolense which cause fatal nagana disease in
domestic ruminants, but are relatively non-pathogenic to the native wild ruminant
population, thus hindering the introduction of exotic species to this habitat (Bowman et al.,
2003).
Another parasite mediated effect within ecosystems is that of manipulation of prey species.
It is perhaps well recognised that predators regulate prey population size but what is not
acknowledged is the role parasites potentially play in this interaction. Parasites with
complex indirect life cycles often rely on their intermediate host being consumed by a
predator in order to complete their life cycle (Choisy et al., 2003; Poulin, 2007). As a
means to increase the chances of reproduction some parasites appear to have adopted
methods of manipulating the behaviour of the intermediate host enabling easier capture by
predators. Temple (1987) conducted a study comparing levels of parasitism in prey items
caught by a tame hawk and those he shot with a gun. He found that prey captured by the
Chapter 1 - Introduction
10
hawk had higher intensity and prevalence of trematodes, nematodes and ectoparasites, than
those shot and suggested parasitism was involved in mediating easier capture by the hawk.
Several studies have since attempted to identify the mechanisms by which parasites are
able to achieve this. One example of this involves the cestode, Echinococcus. The
metacestodes of Echinococcus spp. cause hydatid disease in the intermediate host, usually
a herbivore, through the formation of cysts in the hosts organs (Thompson and Lymbery,
1988). These cysts can often form in the lungs, greatly reducing the animals’ ability to
evade capture by a predator which is the definitive host for this parasite (Fenstermacher,
1937; Cowman, 1947; Joly and Messier, 2004; Barnes et al., 2007). Similar observations
have been made with the coccidian Sarcocystis spp. (Jog et al., 2005; Jog and Watve,
2005). These studies observed that sarcocyst-infected prey (chital deer, Axis axis) were
preferentially taken by the predator (dhole, Cuon alpinus) and although there was no
evidence of clinical signs in the infected prey it was suggested that the large number of
cysts in the heart would compete for oxygen and reduce the ability to evade capture.
Although these examples of parasite mediated increases in predation are often assumed to
be adaptations by the parasite to manipulate prey behaviour, they may simply be by-
products of parasitism. In some cases, however, the adaptive nature of parasite
manipulations has been confirmed. For instance, studies have shown that rats infected with
the protozoan Toxoplasma gondii, display specific behavioural changes that increase the
parasites chances of transmission (Berdoy et al., 2000). Infected rats were found to display
a preference for areas frequented by cats and were therefore vulnerable for predation. The
cat is the definitive host for T. gondii and hence transmission for this parasite was
increased.
Chapter 1 - Introduction
11
1.2.3 Co-extinction events/biodiversity considerations
In addition to the positive and negative effects of parasites on individual hosts and host
populations, there is increasing recognition that parasites are important components of
biodiversity in their own right. Parasites are the single largest component of biodiversity
yet are often ignored by conservation biologists (Windsor, 1998; Poulin and Morand,
2000). Eradication and co-extinction events are severely affecting this biodiversity leading
to possible adverse flow on effects (Koh et al., 2004; Dobson et al., 2008; Colwell et al.,
2009; Dunn et al., 2009). Parasites that are host specific run the same risk of extinction as
their host and this is gaining recognition with studies advocating the need for the
conservation of parasites along with their hosts (Dobson, 1995; Gompper and Williams,
1998; Daszak et al., 2000; Altizer et al., 2003a; Colwell et al., 2009). Dobson et al. (2008)
estimated that the extinction of all species currently listed as threatened by the IUCN Red
List (IUCN, 2010) would lead to the co-extinction of c. 2000 species of helminth parasites.
Given the complexities of host/parasite interactions the loss of any parasite species may
well result in detrimental effects to the host and the ecosystem (Gompper and Williams,
1998).
Besides co-extinction events another risk to host specific-parasites is their eradication in
captive populations. Management of captive animals has a heavy focus on de-worming
programs to ensure maximum health but has the adverse effect of causing possible
extinction of host specific parasites. An example of this is the recovery program for the
black footed ferret (Mustela nigripes). To prevent total extinction of the remaining wild
population, all animals were captured and placed into captivity for later release. During
this time efforts to minimize the threat of disease included the eradication of ectoparasites
Chapter 1 - Introduction
12
within the population. It has since been proposed that a possible species of Neotrichodectes
louse, which was unique to the black footed ferret may now be extinct (Gompper and
Williams, 1998). However, as there was limited baseline information on the parasite fauna
of this host in the wild, positive confirmation of extinction was not possible. This provides
another example highlighting the need for comprehensive data on the parasite fauna of
wildlife hosts, particularly those endangered and being managed through conservation
programs. Criteria for conserving these host-specific parasites may need to be incorporated
into captive breeding programs to maintain the host parasite fauna and levels of immunity
which are present in natural populations (Daszak et al., 2000; Gompper et al., 2003;
Penzhorn, 2006).
1.2.4 Assessing effects of human influences
All of these host/parasite interactions may be further complicated by the effects of habitat
destruction/fragmentation and human encroachment (McCallum and Dobson, 1995; 2002;
Smith et al., 2009a; 2009b). These factors can lead to a disruption of the ‘normal’
host/parasite interactions, with possible detrimental effects to the host (May and Anderson,
1978).
Habitat destruction results in reduced species ranges and increased interactions between
populations, which in turn raises the risk of disease transmission between these populations
(Scott, 1988; Lyles and Dobson, 1993). It can also result in limited resources for viable
populations. The poor planes of nutrition and stress placed on these declining populations
may then result in a rise in parasitic disease. For example, Penzhorn (2006) identified an
Chapter 1 - Introduction
13
endemic stability of the haemoparasite, Babesia spp. in wild populations of lion and
rhinoceros but when individuals of this species were placed under stress, clinical
babesiosis was observed resulting in death of the host.
Perhaps of greater significance is human encroachment and the resultant increased
interaction of humans and their domestic animals with co-habiting wildlife. Approximately
80% of domestic animal pathogens can infect wildlife so the risk of disease spillover into
wild populations is potentially great (Kat et al., 1995; Cleaveland et al., 2001; Applebee et
al., 2005). Examples of this have been documented in populations of the African painted
dog and African lion which have suffered huge population declines due to spillover of
rabies and canine distemper virus (CDV) from domestic dog populations (Kat et al., 1995;
Roelke-Parker et al., 1996). In these cases immunity had not been developed in the wild
population, leaving them open to clinical disease. Another example highlighted by
Gillespie et al. (2005) illustrated the effects of human encroachment in a study on several
primate species living in logged forests compared with those living in unlogged forest.
They identified higher parasite prevalence and richness in populations of the red-tailed
guenon (Cercopithecus ascanius) living in logged forests compared to populations in
unlogged forests. Along with a higher prevalence of parasites species including Trichuris,
Strongyloides and Entamoeba, three additional species were observed in the logged forest
population which were Giardia sp., a liver fluke and Chilomastix mesnili. This study
suggested that the human activity of logging had induced a change in the red-tailed
guenon’s foraging behaviour which in turn increased their exposure to parasites.
Chapter 1 - Introduction
14
In summary, it would appear that parasites play a major role in the natural environment and
are an essential component of any healthy ecosystem (Hudson et al., 2006). Additionally,
these examples provide evidence of the need to increase surveillance of wildlife and build
an extensive database of natural parasitism within wild populations from which a baseline
can be formed. This will assist in the ability to identify potential emerging disease
processes which may pose a threat to wildlife and should become an essential component
in any wildlife management program.
1.3 The host, the African painted dog (Lycaon pictus)
Understanding the ecology of the host is important when attempting to understand
parasitism within that host. Factors such as diet, behaviour and habitat provide insight into
the spectrum of parasite fauna likely to exist within these populations.
The African painted dog (Lycaon pictus), also known as the African wild dog and painted
hunting dog, is an endangered carnivore of sub-Saharan Africa which represents a unique
genus of the canid family, having diverged from the rest of the dog family 3 million years
ago (Girman et al., 1993; IUCN, 2010). Lycaon pictus translates to ‘painted wolf’ in
reference to the mosaic of colours and patterns of the animals’ coat which are unique to
each dog. The last century has seen the population decline by almost 99% from
approximately 300,000 individuals to 3,000-5,500 with viable populations existing in only
a few countries (Fanshawe et al., 1991; Woodroffe et al., 1997; IUCN, 2010). The cause of
their decline has been a combination of human persecution, habitat loss, interspecific
Chapter 1 - Introduction
15
competition and disease (Fanshawe et al., 1991; Woodroffe et al., 1997; Creel and Creel,
1998; Sillero-Zubiri et al., 2004).
1.3.1 Ecology of the African painted dog
African painted dogs are intensely social pack animals spending much of their time in
close association with each other (Woodroffe et al., 1997). They are co-operative breeders
and hunters which make them almost obligate pack animals in that survival outside the
pack is minimal (Jennions and Macdonald, 1994; Creel and Creel, 1995). Painted dogs are
extremely successful hunters and cooperative hunting allows them to bring down large
prey, usually averaging 50 kg but sometimes as large as 200 kg (Malcolm and van Lawick,
1975; Creel and Creel, 1995). Their diet consists mainly of antelope such as impala, kudu
and gazelle but may also include buffalo, hares and lizards (Creel and Creel, 2002; Pole et
al., 2004; Hayward et al., 2006). Packs are based on a matriarchal society, with the alpha
female governing pack movements. The alpha female and her chosen alpha male are
usually the only pair to breed, whilst the rest of the pack assist in rearing the pups through
hunting and pup-guarding (Malcolm and Marten, 1982; Creel and Creel, 1995). Studies
suggest that in order to breed successfully packs need to consist of a minimum of five
animals which allows for both hunting and pup-guarding to take place (Courchamp et al.,
2002; Sillero-Zubiri et al., 2004). This requirement indicates that maintaining pack
numbers, rather than individuals, is vital to ensure continuation of the species (Creel and
Creel, 1995).
Chapter 1 - Introduction
16
The African painted dog is a nomadic species with home ranges greater than 2,000 km2.
The only time packs are stationary is during the denning season which is usually for three
months or until the pups are old enough to follow the pack. During the denning season the
pack, hunting diurnally, will return each time to the den to feed the pups by way of
regurgitation of meat that they have consumed.
1.3.2 Conservation issues for the African painted dog
The predominant threat to the African painted dog is conflict with expanding human
populations, specifically through habitat loss, human persecution and introduced disease
(Creel and Creel, 2002; Sillero-Zubiri et al., 2004). The lack of large protected areas
(greater than 10,000 km2) results in packs roaming outside national parks and into conflict
with humans. Subsequently the risk of death and injury is markedly increased due to roads,
where they are commonly killed, being caught in snare lines, which are set by poachers for
bushmeat, and being shot or poisoned by livestock farmers (Fanshawe et al., 1991; van
Heerden et al., 1995; Creel and Creel, 1998; Rasmussen, 1999). Another human/wildlife
conflict issue is that of domestic dogs. Painted dogs are vulnerable to diseases of domestic
dogs such as rabies and canine distemper virus (CDV). Several painted dog populations
have been adversely affected by epidemic outbreaks of these diseases with a possible
extirpation occurring in the Serengeti ecosystem of Tanzania due to the rabies virus
(Alexander and Appel, 1994; Kat et al., 1996; Woodroffe, 1999). As these animals
naturally live at low population densities catastrophic events such as these pose real threats
to their continued conservation (Creel and Creel, 2002).
Chapter 1 - Introduction
17
Measures taken to counteract the dramatic decline in species numbers have included
reintroduction and relocation programs. Currently there are approximately 400 animals in
captivity according to the International Species Information System (ISIS). Many of these
animals have had success in breeding, allowing for possible reintroductions. Few
reintroduction programs, however, have taken place and most have had limited success
(Scheepers and Venzke, 1995; Woodroffe et al., 1997). Some wild populations in South
Africa are being actively managed as metapopulations, which involves translocation of
animals between fenced wild populations to mimic natural immigration and emigration
(Davies-Mosert et al., 2009). Translocation programs are also used to move animals away
from livestock farms, where conflict with farmers is occurring, and back into the relative
safety of national parks.
1.4 Parasites and the African painted dog
As with most wildlife species, there has been only limited research on the parasites of the
African painted dog. In order to obtain a better understanding of the host/parasite
relationship it is beneficial to understand the ecology of the host, obtain data on similar
species and most importantly conduct longitudinal studies over several populations.
1.4.1 Host ecology and parasites
Parasitism is often heavily influenced by the ecology of the host, as the parasite will have
adapted its life cycle according to host diet, behaviour and habitat. The African painted dog
is a carnivore and therefore exposure to parasites will often be through ingested prey
Chapter 1 - Introduction
18
species. These can act as intermediate hosts for parasites such as members of the cestode
family Taeniidae, and the protozoans Toxoplasma gondii and Sarcocystis spp. Hunting in
packs will see all individuals exposed to the same infected prey species. Additionally, as
they are extremely social animals, other parasites requiring direct transmission between
hosts such as Ancylostoma spp., Giardia spp. and ectoparasites will be easily transmitted
between pack members (Altizer et al., 2003a). This would be especially important during
the denning period when environmental contamination with parasite stages increase and
subsequently transmission rates of these parasites between individuals would also increase
(Altizer et al., 2003b). Evidence for this has been seen with rabies virus epidemics which
have wiped out entire packs (Kat et al., 1996). Finally, as these animals have large home
ranges, packs will often move outside the park borders and through human communities,
thereby raising the risk of them contracting exotic pathogens from domestic dogs (Creel
and Creel, 2002).
1.4.2 Parasites recorded from the African painted dog
The dramatic decline of the African painted dog has lead researchers to focus on ecological
factors such as pack dynamics, the effects of human/wildlife conflict and habitat
fragmentation. The majority of information regarding the parasite fauna of the African
painted dog comes from one study conducted in the early 90’s (van Heerden et al., 1994;
van Heerden et al., 1995). This involved the sampling of 46 animals in Kruger National
Park over three one-week periods and information recorded on the presence of parasites
from blood and faecal samples. The GI parasites that were reported consisted of Taenia sp,
Ancylostoma caninum and an unknown ascarid species. Toxascaris canis was also reported
Chapter 1 - Introduction
19
but this species name is incorrect and was most likely Toxocara canis or Toxascaris
leonina. The haemoparasites reported included Dipetalonema reconditum (microfilariae),
Hepatozoon sp. and Babesia sp. Apart from these studies, there have been incidental
reports resulting from necropsy or parasite specific studies. Young (1975) observed E.
granulosus from one dog in Kruger National Park, Bwangamoi et al. (1993) found
Sarcocystis-like organisms in three animals which had died from rabies. Colly and Nesbit
(1992) reported the death of a painted dog pup due to acute babesiosis. Babesia sp. and
Hepatazoon sp. were also reported by Nietz (1965), Peirce et al. (1995) and more recently
Matjilla et al. (2008). The natural history and importance of these parasites is described in
more detail in Table 1.2.
Table 1.2 A brief natural history of parasites observed in the African painted dog.
Parasite species Transmission Description/lifecycle Importance
Ancylostoma sp. Direct ingestion or skin penetration of infective larvae
Small nematode in the small intestine of the host, which hooks onto the host and sucks blood
Severe anaemia may result in death of host. Possible zoonosis
Taenia sp. Indirect. Intermediate host, usually a herbivore
Large tapeworms in the gut of the definitive host. Gravid proglottids expelled onto pasture and ingested by the intermediate host
Possible intestinal obstruction of definitive host. Intermediate host may be compromised due to cysts forming in organs. Possible zoonoses
Echinococcus sp. Indirect. Intermediate host, usually a herbivore
Small tapeworms in the gut of the definitive host. Gravid proglottids expelled onto pasture and ingested by the intermediate host
Non pathogenic to the definitive host. Causes hydatid disease in the intermediate host. Zoonosis
Toxocara sp. Direct. Ingestion of infective stage
Large roundworms in the intestine of the host
Larval migrans may cause liver and lung damage. Possible zoonoses
Babesia sp. Indirect. Transfer from tick species during a bloodmeal
Protozoan found in blood cells of the host
Anaemia and/or neurological disease causing death
Chapter 1 - Introduction
20
Hepatozoan sp. Indirect. Transfer through ingestion of infected tick
Protozoan in various tissues and white blood cells of the host
May cause sub-clinical disease in the host
Sarcocystis sp. Indirect. Intermediate host, usually a herbivore
A protozoan in the gut of the definitive host
Non-pathogenic to the definitive host. May cause disease in the intermediate host
Dipetalonema reconditum
Indirect. Transfer from flea or louse
A small nematode in the connective tissue of the host. Also microfilariae in the blood stream which are taken up by vector during a blood meal
Non-pathogenic to the definitive host
1.4.3 Gaps in current knowledge of parasitism in the African painted dog
The studies referred to above, whilst beneficial, only provide a ‘snap shot’ of parasitism
within this endangered carnivore. Perhaps the most significant gap in knowledge is that of
comprehensive baseline data which document the prevalence and intensity over time of
parasitism within wild populations (Bjork et al., 2000; Mathews et al., 2006; Smith et al.,
2009a). The single random sampling studies commonly undertaken are not able to identify
temporal or spatial variation of parasitic infection within the natural environment (Bjork et
al., 2000). Longitudinal studies are required to obtain this information, which would then
help to determine which potentially pathogenic agents to monitor within natural
populations (Mathews et al., 2006; Smith et al., 2009b). Increasingly, there is recognition
of the need for good surveillance of native fauna, which draws upon data from related
species and uses longitudinal monitoring to identify and predict the parasites and
pathogens of most importance (De Leo and Dobson, 2002; Smith et al., 2009b). Few
studies have achieved this and to date none have been conducted on the African painted
dog.
Chapter 1 - Introduction
21
1.5 Management of wild species
Human involvement has become pervasive in the management of nearly all wild species.
Most common is the management of wild animals in captive environments where the focus
is on maintaining breeding populations and genetic diversity with the view to eventually
reintroducing these animals to the wild. Management of wild populations has also
increased as suitable habitat continues to decline and the use of translocation programs is
required to move animals away from human conflict areas. Within both these management
environments detailed knowledge of the ‘natural’ parasite fauna of a particular host may
assist conservation efforts by monitoring for disease outbreaks, identifying exotic
pathogens and perhaps allowing for natural immunity against some parasites (Phillips and
Scheck, 1991; Gompper and Williams, 1998; De Leo and Dobson, 2002).
1.5.1 Captive environments
In wildlife facilities with good veterinary practices, animals are more likely to be exposed
to fewer parasites than their wild relatives. However, relatively low levels of parasitism
may still result in clinical disease, as captivity places stress on wild species, which may
affect the functioning of immune systems. Contrary to this, whilst complete eradication of
parasites in captive populations is beneficial to the animal in the short term, this may later
lead to under developed immune systems and a subsequent greater risk of clinical disease
when exposed to pathogens (Windsor, 1997; Gompper and Williams, 1998; Penzhorn,
2006). Additionally, intensive housing, modern, grassy enclosures and mixed species
enclosures may increase the opportunity for parasite transmission between species. On
occasion, the parasites causing clinical disease are not a natural parasite of the species but
Chapter 1 - Introduction
22
result from co-habiting with other species, cross-contamination from other enclosures, and
modified behaviours commonly displayed in captive animals. For example, the tree
browsing giraffe (Giraffa camelopardalis) when kept in modern, grassy enclosures will sit
down and graze (Boomker et al., 1986; Garijo et al., 2004); this modified behaviour
exposes them to parasites from the pasture that they would not normally encounter.
Fukumoto et al. (2004) reported the death of a giraffe due to a heavy infection of the
nematode Camelostrongylus mentulatus, which is only obtained during grazing. This was
compounded by the fact that the giraffe were housed together with camel and antelope, the
natural hosts for this parasite.
Reports such as these, investigating unexpected deaths, are generally how parasitism is
identified in captive environments. There are very few studies directly comparing
parasitism among captive and wild populations. Muller-Graf et al. (1999) conducted a
study on wild populations of lions and then made comparisons with retrospective reports of
parasites in captive populations. Mas Bakal et al.(1980) investigating Toxoplasma gondii,
made direct comparisons between captive and wild animals in Kenya, and Phillips and
Scheck (2001) compared captive and wild populations of red wolves during a
reintroduction program. Whilst it is intuitive that there will be differences between the two
environments, studies documenting specific differences in parasite prevalence and
diversity remain elusive. Data such as these may greatly benefit facilities which use captive
breeding and reintroduction programs as a conservation tool.
Chapter 1 - Introduction
23
1.5.2 Reintroduction programs
If when reintroducing captive bred animals into their wild environment, the type of parasite
pressure to which the host is likely to be exposed is known, then measures can be
undertaken to reduce this impact. A simple example of this was documented in a study on
reintroducing captive bred red wolves (Canis rufus). Phillips and Scheck (1991) noted that
it was beneficial to conduct reintroduction programs during winter when the tick burden
was not as high, as in summer animals appeared to suffer from high infestations and this
apparently reduced the success of the program. Pre-exposure to parasites or maintaining
low levels of ‘natural’ parasite fauna within captive animals may limit the effect of the
substantial parasite challenge they will face in wild environments (Viggers et al., 1993).
For example, when the last remaining population of black footed ferrets (Mustela nigripes)
were taken into captivity, infections with the protozoan parasite Eimeria sp. were allowed
to persist in order for the host population to maintain immunity for eventual release into
the wild (Williams et al., 1992). Additionally, there is a risk of introducing exotic parasites,
which animals have acquired from their captive facilities, into naïve wild populations
(Viggers et al., 1993; Cunningham, 1996). However, without detailed knowledge of what
parasites are naturally found in the wild environment this would be difficult to predict and
prevent.
1.5.3 Translocation programs
As with reintroduction programs the translocation of wild animals from one area to another
may pose the risk of introducing exotic disease to either the existing population or the
translocated animals (Davidson et al., 1992; Cunningham, 1996; Wyatt et al., 2008).
Chapter 1 - Introduction
24
Translocation is quite often a necessary tool for moving animals away from high
human/wildlife conflict areas, stocking depleted populations or in the management of
metapopulations (Davidson et al., 1992; Davies-Mosert et al., 2009). Again, having
extensive baseline data on the parasite fauna of hosts in their natural environment in
different geographic regions will help identify any risk of introducing possible pathogens
to either population during these events (Cunningham, 1996). Cases of introducing exotic
disease from translocation have often had devastating effects. Examples include the co-
introduction of rinderpest with domestic cattle into East Africa which devastated the native
ungulate population, and the protozoan (Myxobolus cerebralis) which causes whirling
disease in trout and is believed to have been introduced from stocked European trout into
native North American rainbow trout (Oncorhynchus mykissi) (Dobson, 1995; Bergersen
and Anderson, 1997).
These examples provide evidence for the need to increase surveillance of wildlife and to
build an extensive database on natural parasitism within wild populations from which a
baseline can be formed. This will assist in the ability to identify potential emerging disease
processes which may pose a threat to wildlife.
1.6 Goals for this study
Using the African painted dog as a model, this study aims to highlight the importance of
obtaining comprehensive data on parasite biodiversity within an endangered species.
Longitudinal data obtained from several wild populations will provide a baseline on which
further studies can build. Individual animal data such as sex, age and social status, when
Chapter 1 - Introduction
25
available, is used to identify susceptibility to parasitism at the individual and population
level. Additionally, environmental factors such as season or geography are incorporated
into the analysis to determine if these are influential in the overall dynamics of parasitism
within the natural environment.
To complement these data, the use of molecular tools will enable species identification,
which has not been possible with traditional microscopy techniques. In many cases,
molecular characterisation of parasites from faecal samples can eliminate the need for
species identification from adult worms, which are usually only obtained during necropsy
of animals. As the host involved in this study is endangered and obtaining animals for
necropsy is almost impossible, these non-invasive methods provide the only way to gain
further insight into the parasite fauna they harbour. Identification of parasite species will
help to ascertain which are host specific, pathogenic, zoonotic or exotic to this species.
It is hoped that this information will assist in the conservation of the African painted dog in
several ways:
providing a comprehensive database on the natural parasitism of Lycaon pictus
which will help identify exotic, zoonotic and emerging diseases within wild
populations.
recognising challenges of parasite control and management within captive
populations
understanding the risks associated with reintroducing parasite-naïve animals into
their natural environment
Chapter 1 - Introduction
26
understanding the risks of introducing exotic parasites between populations during
translocation and reintroduction programs
Identifying parasite fauna existing in the natural environment which may become
pathogenic within the host if/when exposed to environmental stressors.
These goals are addressed within the thesis in the following ways:
Chapter 2 details the general research methods utilized throughout the project.
Chapter 3 identifies the prevalence and diversity of parasites within wild and captive
populations, whilst ascertaining significant effects of host sex and age, and environmental
conditions of season and geographical region.
Chapters 4, 5 and 6 address specific parasite threats. Identification through molecular
characterisation will allow species identification and an understanding of species
distribution among hosts and populations. These methods also assist in identifying any
health risks posed to either the host or surrounding human communities within both
captive and wild environments.
Chapter 7 discusses the main findings with reference to the goals identified in Chapter 1.
Chapter 2 – General materials and methods
27
Chapter 2
General materials and methods
Chapter 2 – General materials and methods
28
2.1. Study design
A parasitological study was conducted on the African painted dog (Lycaon pictus) from
both captive and wild populations. Collaborations were established with three captive
animal facilities and three in situ conservation groups within Africa. The captive
populations were housed in a range of environments including a free range savannah, zoo
exhibit style and a rehabilitation/breeding centre. The wild populations were situated in a
range of geographic locations within Africa. This range of facilities and locations was
chosen in order to get a broad sample base from which variations in parasite prevalence
and diversity may be identified.
These collaborations were crucial to the success of this project, as they allowed for
continual sampling to occur from a range of environments. These associations also
provided the opportunity for additional sampling during radio collaring and/or non-related
veterinary events, whereby skin and blood samples could be obtained along with faecal
samples. The majority of samples were collected during project field trips, however, some
samples were collected by collaborators in the field during their own monitoring season.
Sampling was conducted over the three years of the project (2007-2009) with the exception
of samples from Zimbabwe which had been collected previously in 2006. Most
populations were sampled on multiple occasions during the study period. This sampling
protocol was aimed at achieving longitudinal data from a range of environments in order to
obtain a detailed baseline from which comparisons could be made.
Chapter 2 – General materials and methods
29
2.2 Captive populations
The captive populations were located at Monarto Zoo in South Australia, Perth Zoo in
Western Australia (Figure 2.1) and DeWildt Wildlife Trust in South Africa (Figure 2.5).
Figure 2.1 Location of painted dog study sites within Australia.
2.2.2 Perth Zoo
Perth Zoo is a traditional zoo exhibiting animals in enclosures designed to be similar to the
wild environment. The facility had a painted dog population of 17 animals: 12 males which
were in the on-display exhibit and five females which were kept separately off-exhibit to
prevent unplanned breeding. The on-display exhibit was a large sandy area (1550 m2) with
large trees for shade and a small pond water feature (Figure 2.2). The off-exhibit area was
smaller (480 m2) but also sandy with large trees for shade. All animals were given
= Perth Zoo, Western Australia
= Monarto zoo, South Australia
Chapter 2 – General materials and methods
30
ivermectin monthly as a heartworm prophylaxis. Praziquantel had previously been given as
a preventative treatment for Taeniidae infections but medication with this drug had been
halted a year before this project began. The painted dog diet consisted mainly of horse
meat and the occasional sheep carcass which had been previously frozen. The three eldest
animals were captive born and originated from DeWildt Wildlife Trust in South Africa.
The remaining 14 animals were the result of two litters born at Perth zoo. Samples were
collected from both male and female exhibits annually over the three years prior to the
monthly ivermectin treatment in November 2007, 2008 and 2009. A total of 43 faecal
samples were collected and analyzed from the 17 animals over the three year period. Data
collected annually were used to make comparisons within that population, however, data
from 2007 only were used when making comparisons between populations to avoid
including multiple samples from the same animal.
Figure 2.2 Painted dog exhibit at Perth Zoo showing the water feature and animals resting
in the shade.
Chapter 2 – General materials and methods
31
2.2.3 Monarto Zoo
Monarto zoo is an open range safari style zoo located in South Australia. The facility had a
total of 33 animals: 20 males which were in the on-display exhibit and 13 females which
were kept separately off-exhibit to prevent unplanned breeding. The on-display exhibit
area was a large (8 km2) open savannah style which visitors drove through on zoo buses
(Figure 2.3). The off-exhibit was a much smaller sandy area of approximately 500 m2.
Regular anthelmintic treatments were given to prevent parasitic infections however actual
the anthelmintics used is unknown. The painted dog diet consisted mainly of kangaroo and
horse meat which had been previously frozen. The three eldest animals originated from
DeWildt Wildlife Trust with the remaining animals being the result of litters born at the
zoo. Faecal samples were collected from this facility once in May 2008. It is not known
how recently anthelmintic treatment had occurred prior to sample collection. A total of 34
faecal samples were collected randomly by keepers during routine cleaning of enclosures.
Figure 2.3 Painted dog exhibit at Monarto zoo showing the animals in the large fenced
enclosure.
Chapter 2 – General materials and methods
32
2.2.3 DeWildt Wildlife Trust
DeWildt Wildlife Trust is a breeding and rehabilitation centre for cheetah and African
painted dogs located in Pretoria, South Africa. The facility had approximately 80 African
painted dogs which were housed in up to 25 different enclosures. Enclosures held between
one and six animals made up of various mixes depending on compatibility of animals and
breeding requirements. Enclosures were of varying sizes, ranging from approximately 500
m2 to 1,500 m2, mostly grass covered and with trees for shade (Figure 2.4). Animals were
treated with fenbendazole every four months as a preventative treatment for roundworm,
hookworm and tapeworm. Diet consisted mainly of previously frozen whole chickens and
horse meat with Iams dry dog food. Some animals originated from the wild having been
translocated from livestock farms where they were at risk of being shot. The remaining
population was the result of litters born at the facility. Samples were collected from this
facility once in December 2007, which unfortunately was just after the quarterly
anthelmintic treatment with fenbendazole.
Figure 2.4 Painted dog enclosure at DeWildt Wildlife Trust showing grassy and shady
environment.
Chapter 2 – General materials and methods
33
2.3 Wild populations
The wild populations were located in South Luangwa National Park, Zambia, Nyae Nyae
Conservancy, Namibia and Hwange National Park, Zimbabwe (Figure 2.5).
Figure 2.5 Locations of the painted dog study populations within Africa.
2.3.1 South Luangwa National Park – Zambia
Zambia is a land-locked country situated in central sub-Saharan Africa (Figure 2.5). South
Luangwa National Park is situated at the tail end of the Great Rift Valley and has an area
of 9,050 km2. It is the second largest park in Zambia having been officially proclaimed in
1972 mainly in order to conserve the endemic Thornicroft’s giraffe (Giraffa
camelopardalis thornicroftii). The Luangwa River acts as the eastern border of the park
and is home to large populations of hippopotamus and crocodiles. The park has
= South Luangwa National Park, Zambia
= Hwange National park, Zimbabwe
= Nyae Nyae Conservancy, Namibia
DeWildt Wildlife Trust, South Africa
Chapter 2 – General materials and methods
34
populations of lion, spotted hyaena, leopard and various game animals. The vegetation of
the park is a mosaic of mopane, miombo woodland, acacia and grassland (Figure 2.6).
There are two main seasons within Zambia, the dry season from May to November and the
wet season from December to April.
Figure 2.6 South Luangwa National Park, Zambia. Open grassland area with acacia and
mopane woodland in the background, which is typical of the habitat frequented by painted
dog populations.
The population of African painted dogs within South Luangwa National Park is estimated
at 200 (pers comm. E Droge, Zambian Carnivore Project). Field trips were conducted in
collaboration with the Zambian Carnivore Project, a conservation group based in South
Luangwa National Park. Field agents from this project continually monitor populations of
the African painted dog and other carnivores in order to conserve these species and their
habitats. Samples were collected during field trips in October 2007, June 2008 and May
2009 with occasional sampling between field trips by Zambian Carnivore Project staff
Chapter 2 – General materials and methods
35
during their monitoring periods of painted dog packs in and around the national park.
Where possible a GPS radio collar was placed on an individual within a pack in order to
follow pack movements and ascertain roaming areas. This greatly increased the chances of
locating packs and collecting faecal samples for this project.
2.3.2 Nyae Nyae Conservancy – Namibia
The Nyae Nyae Conservancy is situated in the north eastern corner of Namibia east of
Tsumkwe district (Figure 2.5). It is not a national park but a conservancy area for some of
the last remaining San Bushmen, of the Ju’\Hoansi group. The area is approximately 8,900
km2 and contains a population c.3,000 of predominantly San Bushmen who are traditional
hunter gatherers. The area has populations of hyaena, leopard and a small population of
lion, along with various game animals. The habitat is semi-arid savannah with no perennial
surface water (Figure 2.7), therefore wildlife are reliant on the few water holes existing
throughout the dry season of April – October. A wet season exists from November to
March.
Figure 2.7 Nyae Nyae Conservancy, Namibia. One of the few sandy roads available to
use, surrounded by thick grass and acacia trees.
Chapter 2 – General materials and methods
36
Apparently 75 painted dogs are found in the Tsumkwe area (Lines, 2009). Field trips were
conducted in collaboration with the Wild Dog Project a conservation group conceived in
2002 by the Namibian Nature Foundation in response to a growth in local human/painted
dog conflict. The main aim of the Wild Dog Project is to increase the understanding of
interactions between African wild dogs and humans and finding ways of mitigating
conflict and persecution (www.nnf.org.na/wilddogproject.htm). Samples were collected
during a field trip in July 2008 in conjunction with the Wild Dog Projects own monitoring
period of painted dog packs in the area. Additional sampling was conducted throughout the
monitoring seasons of 2007 and 2008 by Wild Dog Project staff. Some packs had an
individual fitted with a GPS collar, therefore radio-tracking was possible. However,
locating packs within this area was difficult even using telemetry as the flat terrain greatly
reduced signal range and there were minimal roads available to use.
2.3.3 Hwange National Park – Zimbabwe
Zimbabwe is located just below Zambia and is also a land-locked country (Figure 2.5).
Hwange National Park is Zimbabwe’s premier park and is situated in the north east corner
of Zimbabwe, bordering Botswana. The park has populations of lion, spotted hyaena,
leopard and various game animals. The vegetation of the area is a mosaic of miombo
woodland, acacia and open vlei areas (Figure 2.8). Seasons are similar to Zambia with a
dry season from May to November and a wet season from December to April.
Chapter 2 – General materials and methods
37
Figure 2.8 Game managed area of Hwange National Park, Zimbabwe. Open area with
miombo woodland and acacia in the background, typical for painted dog habitat.
A field trip was conducted in May 2009, in collaboration with the Painted Dog
Conservation group which continually monitors populations of painted dogs in and around
adjacent game managed areas of Hwange National Park. Some packs had an individual
with a GPS collar, therefore radio-tracking was possible, however during this field trip no
painted dog packs were located. Although no samples were collected during this time
faecal samples had been stored from previous collections of which a portion collected in
April 2006 were made available for this study.
2.4 Sampling methodology
The majority of samples obtained for this project were faecal samples. This is a non-
invasive method of obtaining biological data from wild animals and has been used for
several previous parasitological studies on wildlife (Muller-Graf, 1995; Marathe et al.,
Chapter 2 – General materials and methods
38
2002; Engh et al., 2003; Smith and Kok, 2006). Non-invasive methods are particularly
useful when dealing with endangered animals. Faecal samples can provide information on
many parasites inhabiting the gastro-intestinal tract including helminths and protozoans.
Additionally, the application of molecular tools increases the information that can be
obtained from these samples.
2.4.1 Ethics and permits
Animal ethics approval was obtained from Murdoch University Animal Ethics Committee
(permit number R2087/07) for the collection of samples including faeces, blood and
ectoparasites from all captive and wild populations of the African painted dog involved in
this study. Additionally the project obtained separate ethics approval from Perth
Zoological Parks Authority Animal Research and Ethics Committee (Project number,
2007-18; reference ZA/3149025776) for the collection of samples from the painted dog
population at that facility.
Permits were obtained from the Zambian Wildlife Authority to conduct research on
parasites of African wild dogs within South Luangwa National Park and adjacent Game
Management Areas. Permits were also obtained from the Ministry of Environment and
Tourism to conduct research and collect samples from the African painted dog populations
in the Kavango and Caprivi regions of Namibia (Permit number 1297/2008). Government
permits were not needed for Zimbabwe as faecal samples obtained had been collected
previously by other researchers with the required documentation.
Chapter 2 – General materials and methods
39
2.4.2 Locating packs
Conducting studies on wildlife can be logistically difficult as finding and tracking animals
within the wild environment is often challenging. The African painted dog has a large
roaming area (>2,000 km2) and is particularly hard to visually locate due to the colour and
pattern of each animals coat, which act as excellent camouflage. During the day, packs are
inactive and are usually resting under trees or scrub and are difficult to locate. Radio
tracking was therefore crucial to locate packs on any given day. Most packs within the
study population had at least one animal radio-collared, which was usually sufficient to
locate the rest of the pack. Radio-tracking was most successful when the packs were on the
move as there was more chance they would move into the main game area and within
telemetry range. This was usually when the packs were hunting which occurs in the
morning and evening. Tracking in the morning was usually from 5am to 11am and in the
afternoon from 3pm to 8pm, however, if it appeared the packs had moved from the vicinity
of base-camp it was necessary to conduct longer searches, whereby the entire day was used
for tracking. Occasionally this also required several days camping in the bush to continue
the search in that area. On occasion a light aircraft was used to radio-track from the air
which enabled the search grid to be greatly expanded.
When the packs were located, they were identified by compiled indentikits. Coat patterns
are unique for each animal and are used as a means of identification. Animals therefore had
both left and right sides of their torso photographed. Identification numbers were allocated
to each animal within each pack and used for later identification in the field (Figure 2.9).
Chapter 2 – General materials and methods
40
Figure 2.9 The left and right side views of an individual painted dog from the Katete pack
in Zambia. ID number P3 0308.
2.4.3 Sample collection
Sample collection in the wild environment involved locating and following packs and
picking up faecal samples as dogs defecated. Faecal samples were placed in a ziplock bag
and kept in a cooler box until return to camp. On return samples were placed into 2 x 10 ml
centrifuge tubes and fixed in 70% ethanol and 10% formalin. Tubes were labelled with
date, place collected, pack name and where possible individual animal identification. Many
times it was not possible to identify individual animals due to the fast movements of
animals as they rouse for a hunt or to interference from safari vehicles. Pack identification
however, was usually obtained. During field trips three animals were anaesthetised in order
to place a radio-collar, and in this case it was possible to obtain blood samples, check for
ectoparasites and obtain faecal samples direct from the animal. Samples of blood were
stored on FTA cards and a smear placed on a microscope slide, while ectoparasites were
placed in 70% ethanol.
Chapter 2 – General materials and methods
41
Sample collection within the captive environment involved walking through enclosures
and collecting faecal samples from the ground. Individual animal information was
therefore not possible in most cases. At Perth zoo however, it was possible to get
individual samples with the use of non-toxic plastic beads to act as faecal markers for
individual dogs. With the help of keepers all animals were fed meat parcels (horsemeat)
which had had coloured plastic markers (1 tsp) inserted into a pocket cut into the meat.
Animals were brought into the night quarters where they could be separated, identified and
handfed the parcel of meat. Colours given to each animal was recorded in order to match
scat samples collected in the next 24-48 hours. This method has been used with success in
several studies on both wild and domestic animals (Delahay et al., 2000; Rolfe et al., 2002;
Staniland, 2002; Hernot et al., 2005).
2.4.4 Sample movement
The appropriate permits were obtained to export samples from Africa to Australia. A
permit (number 73453) was obtained from Ministry of Environment and Tourism for
samples sent from Namibia. Permits (numbers not given) were obtained from the
Department of Veterinary and Livestock Development for each shipment of samples sent
from Zambia.
AQIS permits to import fixed faecal samples into Australia were not required providing
specimens were preserved in either 70% ethanol or 10% formalin and containers were
sealed and packaged correctly. This ensured all pathogens were killed and the risk of
unforseen leakage was contained. Samples were stored in 10 ml centrifuge tubes fixed in
Chapter 2 – General materials and methods
42
the appropriate preservative (70% ethanol or 10% formalin). These tubes were then
wrapped in absorbent cotton material and placed inside two plastic coverings. These were
then boxed and sent with copies of the appropriate export and import documentation for
each country. All packages were sent through international shipping companies as
‘dangerous goods in accepted quantities’ packages to Murdoch University.
2.5 Parasitological techniques
Analysis of fresh faecal samples was preferred as parasite ova are more readily observed
under microscopy, however, for quarantine reasons samples had to be preserved in a
fixative. Faecal samples fixed in 10% formalin (2 parts faeces, 8 parts formalin) were
deemed the preferred fixative for microscopy (Foreyt, 2001). Samples fixed in 70%
ethanol were used for molecular characterisation.
2.5.1 Microscopy; qualitative analysis
Identification of parasite ova from faecal samples was made on size and morphology with
reference to Foreyt (2001) (Figure 2.10). The coccidians observed were unable to be
differentiated on size alone and as samples were preserved in 10% formalin oocyts, were
not able to be sporulated for additional morphological information. Additionally,
carnivores are commonly known to exhibit spurious coccidian infections originating from
ingested prey items further complicating identification (Bowman et al., 2003). However,
whilst it was recognized that some observations of coccidia may not be true infections, it
was impossible to ascertain which were not spurious, therefore all positive samples were
Chapter 2 – General materials and methods
43
included in the prevalence data. In an attempt to observe all parasites existing within each
sample three techniques were employed: Malachite green stain, zinc sulphate flotation and
sodium nitrate flotation.
Figure 2.10 Parasite ova of taeniid spp. and Giardia spp. cysts observed during
microscopy analysis of painted dog faecal samples. Morphology and size are substantially
different between the two genera, allowing for unambiguous identification.
The malachite green stain was based on a simple faecal smear but with a drop of 5%
malachite green added which enabled parasite ova, particularly Cryptosporidium oocysts,
to be more readily observed (Elliott et al., 1999). Flotation techniques are commonly used
to recover parasite eggs and oocysts from faeces and are designed around differences in
specific gravity of parasite ova and faecal debris within specific flotation media (Bowman
et al., 2003). Most parasitic stages float at a specific gravity of 1.2 to 1.3 whilst faecal
debris will sink (Foreyt, 2001). As some parasite ova are heavier (eg. Trichuris sp. ova)
and formalin fixing can alter the normal buoyancy of eggs, two flotation media were used,
sodium nitrate with a specific gravity of 1.27 and zinc sulphate with a specific gravity of
1.18 (pers comm. A. Elliott). Sodium nitrate was used with the commercially available
Faecalyzer® tubes as gravitational force alone was sufficient for eggs to float within this
Chapter 2 – General materials and methods
44
medium (Bowman et al., 2003). A small amount of faecal sample was placed into the tube
which was then filled with sodium nitrate and left for 10 minutes. A coverslip placed on
top of the tube collected the parasite ova which had floated to the top and was then used for
microscopy. Zinc sulphate was used for the remaining sample with 2 g of faeces placed
into a 10 ml centrifuge tube, emulsified in the flotation medium and centrifuged at 2,000
rpm for five minutes. This method concentrated all parasite ova into the top layer of the
tube where a wire loop was used to collect 5 drops of fluid from the meniscus and placed
onto a microscope slide for analysis. Three slides containing blood smears were to be
analysed for the presence of haemoparasites such as Babesia spp. using microscopy,
however, before this could be done slides were lost. Results for ectoparasites obtained
during the study period were not included in this thesis due to the very small sample size.
2.5.2 Microscopy; quantitative analysis
Quantitative analysis was undertaken by calculating eggs per gram (EPG) of faeces.
Calculating EPG is generally done using a McMaster counting chamber (Foreyt, 2001;
Bowman et al., 2003). The zinc sulphate technique used in this project involved a known
amount of faeces and fluid for each test but the wire loop collection method inhibited use
of a McMaster chamber, therefore alternate calculation methods were devised (pers comm.
R. Dobson). As outlined above, five wire loop drops were placed onto a slide and all
parasite ova and cysts under the coverslip were counted. The volume of the fluid placed
onto the slide was weighed and found to be 0.035 g, coming from the meniscus of the 10
ml tube which was estimated at 0.1 ml. Therefore 1/3 of floated ova and cysts were
Chapter 2 – General materials and methods
45
counted. To obtain EPG the total was multiplied by three (for total meniscus count) and
then divided by 2 (as 2 g of faeces was in each 10ml tube).
2.5.3 Molecular characterisation
As species identification for many parasites is not possible from parasite ova, molecular
techniques were employed to characterise these to species level. As these techniques are
time consuming and expensive only parasite genera considered important from a zoonotic
or pathogenic perspective were chosen. Molecular characterisation was therefore
conducted on faecal samples containing taeniid ova, hookworm ova and Giardia cysts.
Full methodologies for these are found in Chapters 4, 5 and 6. Five blood samples on FTA
cards were sent to a laboratory in South Africa for molecular studies on haemoparasites
such as Babesia spp. but results have not yet been received. These same FTA card blood
samples were tested for the presence of Trypanosoma spp. using molecular methods. All
samples were negative and as there were so few samples, results were not included in the
main body of this thesis.
Chapter 3 – Diversity and prevalence of…..
46
Chapter 3
Diversity and prevalence of gastrointestinal parasite fauna within captive and wild populations
of the African painted dog
Chapter 3 – Diversity and prevalence of…..
47
3.1 Introduction
There are at least as many species of parasites as there are free-living organisms, yet except
for humans and a small number of domesticated plants and animals, little is known about
the diversity and prevalence of parasites existing within host populations (Altizer et al.,
2003a; Mathews et al., 2006; Smith et al., 2009a). It is widely acknowledged that parasites
have the ability to regulate host populations through their ability to influence host
mortality, morbidity and fecundity (May and Anderson, 1978; Scott, 1988; McCallum and
Dobson, 1995; Hudson et al., 1998). Parasites may also mediate predatory and competitive
interactions, host immunity, host genetic diversity and host behaviour (Anderson, 1972;
Carroll and Grove, 1985; Temple, 1987; Altizer et al., 2003b; Maillard and Gonzalez,
2006; Barnes et al., 2007). These factors are important processes within ecosystems and
highlight the significance of parasitism within host populations. To add to these complex
interactions, the effects of outside stressors such as habitat destruction and human
encroachment are important influences which can easily disrupt the natural balance of
many host/parasite relationships (McCallum and Dobson, 1995; McCallum and Dobson,
2002; Gillespie et al., 2005).
The increasing recognition of parasites and their interactions within wildlife hosts has
resulted in additional research, yet comprehensive baseline data are still lacking for many
species of wildlife (Daszak et al., 2000; Applebee et al., 2005; Deredec and Courchamp,
2006; Penzhorn, 2006; Thompson et al., 2010). Most studies on parasitism in wildlife
focus either on understanding the life cycle and pathogenesis of a single parasite species or
taking a ‘one-off’ snapshot of the parasite community existing within a particular host
population. While such studies are useful starting points, of greater benefit would be
Chapter 3 – Diversity and prevalence of…..
48
longitudinal studies of several populations in various geographical regions. This detailing
of temporal and spatial variation of parasitic infections within the natural environment
would provide a baseline from which potential pathogenic changes could be identified
(Bjork et al., 2000). Pathogenic effects may originate from introduced exotic parasites for
which host populations have not developed any level of immunity, for example, the
introduction of rabies and canine distemper virus from domestic dog populations into
African lion (Panthera leo) and African painted dog (Lycaon pictus) populations
(Alexander and Appel, 1994; Kat et al., 1995; Cunningham, 1996; Daszak et al., 2000).
Likewise, enzootic parasites which within a healthy population cause little pathogenicity
could give rise to clinical disease in populations experiencing stressors such as drought,
overcrowding due to habitat destruction or human encroachment (McCallum and Dobson,
2002; Penzhorn, 2006; Munson et al., 2008). Without good baseline data of parasitism
within natural environments these events would be difficult to identify or predict. The lack
of good baseline data is in large part due to the difficulties involved in sampling wild
populations. Locating study animals, obtaining individual identifications and obtaining
samples is time consuming and logistically difficult.
The African painted dog is a highly endangered carnivore with approximately 3,000
animals remaining in the wild (IUCN, 2010). These individuals exist in small fragmented
populations which are vulnerable to stochastic disease outbreaks, leading to local
extinctions as already observed in the Serengeti ecosystem (Kat et al., 1996; Sillero-Zubiri
et al., 2004). It is therefore essential for the future conservation of this animal to gain a
broad understanding of threatening processes, such as parasitism, to which this animal is
routinely exposed.
Chapter 3 – Diversity and prevalence of…..
49
This is the first longitudinal parasite survey of the African painted dog and one of few
existing for any wild species. This project was fortunate in being able to collaborate with
three in situ conservation groups in Zambia, Namibia and Zimbabwe, which were
constantly monitoring painted dog packs within their study area. This enabled
comprehensive sample collection from known individuals and packs over various
geographic regions. By sampling over a period of time in various geographic regions it was
hoped to gain insight into the population dynamics of parasitism within a wild and
endangered carnivore.
The aim of this study was to determine the prevalence and diversity of gastrointestinal (GI)
parasites within captive and wild populations of the African painted dog and relate
measures of parasitism to intrinsic factors such as host age and sex, and extrinsic factors
such as location and season. The following hypotheses were tested: 1) levels of parasitism
are markedly different between captive and wild populations; 2) levels of parasitism are
greater in the wet season than in the dry season in the wild; 3) levels of parasitism are
greater in younger animals and 4) there are geographical differences in levels of parasitism
between wild populations.
3.2 Materials and methods
3.2.1 Sampling protocol
Faecal samples were obtained from three wild populations and three captive populations of
the African painted dog over a four year period, 2006 – 2009. Chapter 2 gives detailed
descriptions of populations sampled. A total of 128 samples were collected from a possible
Chapter 3 – Diversity and prevalence of…..
50
83 individual animals within the wild populations and 104 samples from 130 individual
animals within the captive populations (Table 3.1)
Table 3.1 Number of faecal samples obtained from all captive and wild populations during
the study period.
Population Sampling year Total
samples
Individual
animals
2006 2007 2008 2009
Wild populations
Zambia - 11 44 18 73 43
Namibia - 19 10 - 29 28
Zimbabwe 26 - - - 26 12
Total 26 30 54 18 128 83
Captive populations
Perth - 16 14 13 43 17
Monarto - - 34 - 34 33
DeWildt - 27 - - 27 80
Total 0 43 48 13 104 130
Collection of samples from wild populations was conducted during field monitoring of
packs within the study area. Faecal samples were collected soon after being deposited and
individual animal information was obtained where possible. Within Zambia, most samples
were collected during the periods of November to December 2007, May to June 2008 and
Chapter 3 – Diversity and prevalence of…..
51
May to June 2009, however, a small proportion were collected throughout the year by field
collaborators. Within Namibia, most samples were collected during August to November
2007 and May to November 2008 by field collaborators. Within Zimbabwe, samples were
collected in April 2006 and stored for later analysis.
Collection of samples from captive populations was conducted during cleaning of
enclosures by zoo keepers. A single sampling episode was undertaken in December 2007
for the South African population and May 2008 for the South Australian population. These
samples were obtained randomly from group enclosures. Sampling in Western Australia
was conducted each year in November of 2007, 2008 and 2009. In Western Australia,
sampling of individual hosts was made possible by spiking the animals’ meat with non-
toxic plastic beads which allowed for identification on defecation (see Chapter 2).
Two grams of faecal matter from each sample were placed into two 10 ml centrifuge tubes
containing 8 ml of either 10% formalin for subsequent microscopy analysis or 70% ethanol
for molecular characterisation.
3.2.2 Parasite identification and quantification
See Chapter 2 for a full description of microscopy methods used. All parasite ova, cysts
and larvae were recorded. Eggs and/or oocysts per gram (EPG) of faeces were calculated
as described in Chapter 2 and results used for quantitative analyses. EPG values were not
obtained for Spirometra spp. or Filaroides spp. as these were rare observations. Similarly,
EPG values were not obtained for Giardia spp. as it was found that cysts were especially
Chapter 3 – Diversity and prevalence of…..
52
hard to observe in formalin fixed samples due to desiccation, leading to an under
estimation of intensity.
3.2.3 Host and environmental variables
When age and sex of the host was known, individual data were used for comparisons. Ages
of two years and under were defined as juvenile (n=9) and above 2 years were defined as
adult (n=20). Nineteen samples were obtained from identified males and 13 from females.
All wild sample sites had distinctive wet and dry seasons which were also used for
comparisons. Wet season samples (n=28) were from December through to March and dry
season samples (n=62) from April through to November.
3.2.4 Data analysis
This study examined the differences in parasite prevalence and diversity, intensity of
parasite infection and parasite infracommunity composition within and between captive
and wild populations of the African painted dog.
3.2.4.1 Descriptors used
Descriptors used to quantify parasitism within this study followed Bush et al. (1997) and
Poulin (1993) as follows:
Parasite load (N) is the total number of parasites, of all species, in a single infected
host, i.e. the number of individual parasites in an infracommunity. Parasite load
was measured by the total EPG.
Chapter 3 – Diversity and prevalence of…..
53
Prevalence is the percentage or proportion of hosts infected with one or more
individuals of a particular parasite species or taxonomic group.
Diversity is the number of species of parasites present within specific individuals
and/or groups of hosts. Diversity of parasites was measured by species richness (S)
and the Shannon-Wiener index of species evenness (H).
Infracommunity composition is the number and intensity of species in an individual
host.
Parasite aggregation within host populations is defined as when most hosts harbour
few or no parasites, while only few are heavily infected. Aggregation was measured
by the index of discrepancy (D) using EPG data for a particular species.
3.2.4.2 Levels of testing
Levels of parasitism were firstly tested between wild and captive groups for significant
differences. The data from wild populations were then analysed at the pack and population
(all packs within a national park) level and related to intrinsic factors such as host age and
sex, and extrinsic factors such as geographic location and season (see Table 3.2). For many
comparisons sufficiently large sample sizes could only be obtained by pooling data over
age, sex and seasonal classes, or over different packs or populations. Data from year 1
(2007) of the Perth Zoo captive population were pooled with the other two captive
populations for comparison with wild populations. In wild populations, data were pooled
over time when making comparisons as it was found that the composition of packs varied
significantly from season to season with many deaths recorded, consequently duplicate
sampling of individuals was extremely rare. Known duplicates obtained within the same
sampling period were discarded before performing statistical analysis.
Chapter 3 – Diversity and prevalence of…..
54
Table 3.2 A hierarchical list of comparisons made between host groups with descriptions
of the data used at each level.
Comparison Data used for comparison
Between wild and captive populations Data from the three captive populations
were pooled and compared against pooled
data obtained from the three wild
populations.
Among packs Data from two packs within the Zambian
population were pooled over all age, sex
and season classes.
Among populations in different geographic
regions in the wild
Data from Zambia, Namibia and Zimbabwe
were pooled over all age, sex and seasonal
classes in each population.
Among wet and dry seasons in the wild Data were pooled over geographic regions,
age and sex and compared between wet and
dry season.
Among host sex classes in the wild Data were pooled over geographic regions,
season and age and compared between
males and females.
Among host age classes in the wild Data were pooled over all geographic
regions, season and sex and compared
between juveniles and adults.
Chapter 3 – Diversity and prevalence of…..
55
3.2.4.3 Statistical analysis
Prevalences of infection were expressed as a percentage of positive samples found with
95% confidence intervals calculated assuming a binomial distribution, using the software
Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in prevalences between
groups were tested using the Fisher’s exact test.
One way analysis of variances (ANOVA’s) were used to compare species richness (S),
species diversity (H) and parasite load (N) among groups of hosts with the software JMP
4.0 (SAS Institute Inc; www.sas.com).
Similarities in parasite species infracommunity composition among individual hosts were
estimated from EPG data using the Bray-Curtis coefficient. Multidimensional scaling plots
were used to represent these data where a stress value of less than 0.2 was taken to indicate
reasonable representation of rank similarities by the ordination plot (Clarke, 1993). The
significance of differences in parasite species composition between groups of hosts was
tested by a permutation procedure applied to the pair-wise similarity matrix (one-way
ANOSIM) using the computer package PRIMER 6.0 (Clarke and Gorley, 2006). The
contribution of individual parasite species to dissimilarities between variables was assessed
by averaging the Bray-Curtis similarity term for each species over all pair-wise variable
combinations using SIMPER procedure in PRIMER 6.0. Parasite aggregation within hosts
was tested using the index of discrepancy, (D) as per Poulin, (1993) with the software
Quantitative Parasitology 3.0 (Rozsa et al., 2000).
Chapter 3 – Diversity and prevalence of…..
56
3.3 Results
3.3.1 Variation between captive and wild populations
Table 3.3 displays the diversity of GI parasites within all captive and wild populations
sampled. Overall prevalence of infection (i.e. infection with any species of parasite) was
significantly greater in wild than in captive populations (Fisher’s exact test, P<0.0001).
The wild population also had a greater parasite load (N; F=503.1, P<0.0001), species
richness (S; F=213.3, P<0.0001)) and species evenness (H; F=80.9, P<0.0001), (Figure
3.1)
-1
0
1
2
3
4
5
6
7
8
9
N S H
Measures of parasitism
Mea
n v
alu
e
Captive
Wild
Figure 3.1 Parasite load (N), species richness (S) and species evenness (H) in captive and
wild populations of the African painted dog.
Chapter 3 – Diversity and prevalence of…..
57
Table 3.3 The prevalence (with 95% confidence intervals in parentheses) and diversity of GI parasites detected in faecal samples
from all captive and wild populations of the African painted dog.
Population Total parasite
prevalence
(%)
Taxon prevalence (%)
Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides
Captive
n=130
15
0 0 0.8
(0.04 - 4)
14
(6 – 16)
0 0 0
Wild
n=83
99 32
(22 – 42)
32
(23 – 43)
2
(0.07 – 6)
26
(18 – 37)
13
(8 – 24)
99
(94 – 100)
2.4
(0.4 – 8)
Chapter 3 – Diversity and prevalence of…..
58
3.3.2 Variation between packs
Two packs (Katete and Kaingo) within the Zambian study population were sampled
sufficiently to enable comparisons to be made on parasite prevalence, parasite load,
diversity and infracommunity composition. Table 3.4 displays the prevalences of all GI
parasites observed in the Katete and Kaingo packs of South Luangwa National Park,
Zambia. The Katete pack had a significantly greater prevalence of taeniid spp. (Fisher’s
exact test, P=0.005), Ancylostoma spp. (Fisher’s exact test, P=0.002) and Coccidia
(Fisher’s exact test, P=0.005) than that observed in the Kaingo pack. The Katete pack also
had a greater parasite load (N; F=28.4, P<0.0001), species richness (S; F=34.8, P<0.0001)
and species evenness (H; F=41.9, P<0.0001) (Figure 3.2).
Table 3.4 Prevalence (with 95% confidence intervals in parentheses) of GI parasites
detected in faecal samples from two packs within the Zambian study population.
Pack ID Taxon prevalence (%)
Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides
Katete
(n=12)
50
(24-76)
58
(29-82)
8
(0.4-37)
8
(0.4-37)
50
(24-76)
100
(76-100)
16
(3-46)
Kaingo
(n=13)
0 0 0 46
(22-74)
0 100
(77-100)
0
P value 0.005 0.002 0.5 0.07 0.005 1.00 0.2
Chapter 3 – Diversity and prevalence of…..
59
-2
0
2
4
6
8
10
12
14
N S H
Measures of parasitism
Mea
n va
lue
Katete
Kaingo
Figure 3.2 Parasite load (N), species richness (S) and species evenness (H) in two packs
within the Zambian study population.
Infracommunity composition was also found to be significantly different between painted
dogs in the two packs (ANOSIM, R=0.42, P=0.001). This can be clearly seen in the two-
dimensional ordination plot of Bray-Curtis similarity coefficients of parasite
infracommunity composition (Figure 3.3).
Figure 3.3 A multidimensional scaling plot of data from two African painted dog packs
within the Zambian population based on Bray-Curtis similarity coefficients of parasite
infracommunity composition.
Chapter 3 – Diversity and prevalence of…..
60
3.3.3 Variation among different geographic locations
Sampling was conducted in three geographic locations - Zambia, Namibia and Zimbabwe.
Populations in these locations were tested for differences between parasite prevalence,
parasite load, diversity and infracommunity composition. Coccidia were significantly less
prevalent in Namibia when compared with Zambia (Fisher’s exact test, P=0.009) and
Zimbabwe (Fisher’s exact test, P=0.02), however, no significant differences were found in
the prevalence of other parasite species or in the overall prevalence of GI parasite
infections (Table 3.5).
A significant difference in parasite load (N; F=3.2, P=0.04), but not species richness (S;
F=1.1, P=0.3) or species evenness (H; F=0.9, P=0.5), was observed among populations
(Figure 3.4). There were, however, no significant differences in parasite infracommunity
composition among populations (ANOSIM R=0.06, P=0.08).
0
1
23
4
5
6
78
9
10
N S H
Measures of parasitism
Mea
n va
lues
Zambia
Namibia
Zimbabwe
Figure 3.4 Parasite load (N), species richness (S) and species evenness (H) in three wild
populations of the African painted dog.
Chapter 3 – Diversity and prevalence of…..
61
Table 3.5 The overall prevalence (with 95% confidence intervals in parentheses) and diversity of GI parasites detected in faecal
samples from three wild populations - Zambia, Zimbabwe and Namibia.
Population Total
prevalence
(%)
Taxon prevalence (%)
Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides
Zambia n=43 100
(91-100)
35
(22-50)
33
(19-48)
2
(0.1-13)
30
(18-45)
21
(11-36)
100
(91-100)
5
(0.8-16)
Namibia n=28 96
(83-100)
25
(12-45)
43
(26-62)
0 29
(14-48)
0 96
(83-100)
0
Zimbabwe n=12 100
(76-100)
33
(12-63)
8
(0.4-37)
0 8
(0.4-37)
25
(7-54)
100
(76-100)
0
Chapter 3 – Diversity and prevalence of…..
62
3.3.4 Variation between different seasons
All study sites have definite seasonal variation with a wet and dry season. Table 3.6
displays the prevalence of GI parasites obtained from hosts during the wet and dry seasons
pooled over populations from all geographic locations. A significantly greater prevalence
was observed for Ancylostoma spp. (Fisher’s exact test, P=0.03) and taeniid spp. (Fisher’s
exact test, P=0.005) during the wet season.
Table 3.6 Prevalence of the main GI parasites (with 95% confidence intervals in
parentheses) detected in faecal samples from all wild populations in wet and dry seasons.
Season Taxon prevalence (%)
Taeniid Ancylostoma Giardia Coccidia Sarcocystis
Wet (n=28) 46
(28-65)
61
(41-71)
18
(7-36)
18
(7-36)
100
(88-100)
Dry (n=62) 23
(13-35)
27
(18-40)
26
(16-38)
19
(11-31)
98
(91-100
P-value 0.03 0.005 0.6 1.00 1.00
Parasite load (N; F=0.5, P=0.4) was not significantly different between seasons but a
greater level of species richness (S; F=4.7, P=0.03) and species evenness (H; F=5.2,
P=0.05) was observed in the wet season (Figure 3.5).
Chapter 3 – Diversity and prevalence of…..
63
0
1
23
4
5
6
78
9
10
N S H
Measures of parasitism
Mea
n va
lues
Wet
Dry
Figure 3.5 Parasite load (N), species richness (S) and species evenness (H) between wet
and dry seasons in all wild populations of the painted dog.
Community composition was also found to be significantly different between seasons
(ANOSIM R=0.13, P=0.007) as displayed in Figure 3.6. This is shown in the two-
dimensional ordination plot of Bray-Curtis similarity coefficients of parasite
infracommunity composition among populations (Figure 3.6).
Figure 3.6 A multidimensional scaling plot of data from wet and dry environments of
three wild populations based on Bray-Curtis similarity coefficients of parasite
infracommunity.
Chapter 3 – Diversity and prevalence of…..
64
3.3.5 Variation between host age and sex
No significant relationships were identified between host sex and levels of parasite
prevalence (Fisher’s exact test, P=0.3), parasite load (N; F=0.002, P=0.9), species richness
(S; F=1.6, P=0.2), species evenness (H; F= 0.9, P=0.3) and parasite infracommunity
composition (ANOSIM R=0.16, P=0.09).
No significant relationships were identified between host age and levels of parasite
prevalence (Fisher’s exact test, P=1.00), parasite load (N; F=1.2, P=0.3), species richness
(S; F=0.4, P=0.5), species evenness (H; F=1.1, P=0.9) and parasite infracommunity
composition (ANOSIM R=0.01, P=0.5).
3.3.6 Parasite aggregation within hosts
Parasite species from which sufficient EPG data were obtained (Ancylostoma spp., taeniid
spp., coccidia and Sarcocystis spp.) were tested for aggregation within the host populations
of Zambia, Namibia and Zimbabwe. Aggregation of these parasites was observed within
each population by the Index of Discrepancy (D) values. A value of 0 indicates an even
distribution of counts across all hosts and a value of 1 indicates all parasites aggregated in
a single host (Table 3.7).
Chapter 3 – Diversity and prevalence of…..
65
Table 3.7 Aggregation of parasite species within host populations in Zambia, Namibia and
Zimbabwe using the Index of Discrepancy values (D).
Ancylostoma Taeniid Coccidia Sarcocystis
Zambia 0.83 0.81 0.85 0.7
Namibia 0.8 0.84 - 0.72
Zimbabwe 0.85 0.7 0.8 0.51
3.4. Discussion
3.4.1 Parasite diversity
Overall, a total of seven GI parasite genera were observed in the African painted dog. Five
of these genera have not been reported before in this host: Giardia, Spirometra,
Sarcocystis, Isospora and Filaroides.
Table 3.8 GI parasite genera observed in this study and in published literature.
GI parasite genera detected in this study GI parasite genera reported in published
literature*
Taeniid
Ancylostoma
Spirometra
Giardia
Isospora
Sarcocystis
Filaroides
Taeniid
Ancylostoma
Ascarid (species undetermined)
*Young et al., 1975; van Heerden et al., 1994, 1995.
Chapter 3 – Diversity and prevalence of…..
66
The most prevalent parasite genus observed in wild populations of dogs was Sarcocystis
(99%), followed by taeniids (32%), Ancylostoma (32%), Giardia (26.5%), Coccidia (13%),
Spirometra (2.4%) and Filaroides (2.4%). In contrast, only Giardia (14.5%) and
Spirometra (0.8%) were observed in the captive populations.
The high prevalence of Sarcocystis spp. sporocyst in faecal samples suggests that the
painted dog is a natural definitive host for this organism. This finding is perhaps not
surprising considering carnivores are known definitive hosts for species of parasite with
transmission occurring through ingestion of infected prey. Species identification within the
genus Sarcocystis was not made in this study but based on the prey items of the painted
dog and known intermediate hosts, likely species can be suggested. Cosmopolitan species
which have canids as the definitive host include S. arieticanis (sheep), S. capricanis (goat)
and S. cruzi (cattle) and could all be potential sources of infection for the painted dog.
Species with intermediate hosts specific to Africa include S. nelsoni (puku and waterbuck),
S. melampi (impala), S. woodhousi (springbok, dik dik) and S. phacochoeri (warthog)
(Levine, 1986; Odening, 1986). While definitive hosts for these Sarcocystis species are
unknown, the intermediate hosts are known prey items of the painted dog which could
therefore be considered as a possible definitive host (Estes, 1967; Creel and Creel, 1995;
Hayward et al., 2006).
The only previous study reporting this parasite in the painted dog observed Sarcocystis-
like organisms in the musculature and suggested that the painted dog was a natural
intermediate host (Bwangamoi et al., 1993). Whilst carnivores acting as intermediate hosts
for Sarcocystis is rare, schizonts of S. canis, which are normally only present in the
Chapter 3 – Diversity and prevalence of…..
67
intermediate host have been identified in the tissues of domestic dogs (Dubey and Speer,
1991). Sarcocystis is rarely pathogenic to the definitive host, but acute infection in the
intermediate host may cause extensive tissue damage and subsequent increased mortality
and morbidity (Dubey et al., 1989; Bowman et al., 2003).
Taeniids and Ancylostoma spp. were found at the same prevalence of 32% within the wild
populations, which is similar to a previous report of a wild population of the painted dog
(van Heerden et al., 1995). Taeniids are generally non-pathogenic to the definitive host but
heavy infections may lead to possible intestinal obstruction (Foreyt, 2001). Infections with
Ancylostoma can be pathogenic, particularly to young and/or immunocompromised
animals, and deaths due to ancylostomiasis have been recorded in a captive population of
the painted dog (van Heerden et al., 1994; 1996).
Species of Giardia had not been observed in the African painted dog prior to this study,
but this parasite genus is becoming increasingly recognised in populations of several wild
host species (Graczyk et al., 2002; Gompper et al., 2003; Gillespie et al., 2005; Trout et al.,
2006; Thompson et al., 2009). The prevalence observed in this study indicates a substantial
portion of animals in the wild are infected, with unknown clinical effects. This parasite
does have the ability to cause sub-clinical disease, such as growth retardation in hosts
suffering from poor nutrition, which may be of consequence to declining painted dog
packs experiencing lowered hunting success (Astiazaran-Garcia et al., 2000; Courchamp et
al., 2002).
Chapter 3 – Diversity and prevalence of…..
68
Whilst differentiation among the coccidians was not possible for most observations,
Isospora canis was identified on the basis of the large size of the oocysts, separating it
from most other coccidians. This parasite is host specific to canids, indicating a true
infection rather than a spurious observation of parasites from ingested prey species. Heavy
infections can cause severe enteritis, particularly in pups (Bowman et al., 2003). Filaroides
spp. and Spirometra spp. were only observed rarely in this study but these are the first
reports for the painted dog. Spirometra was observed in both captive and wild populations,
while Filaroides was observed only in wild populations.
3.4.2 Influence of geographic, seasonal and demographic factors
Within wild painted dogs there were some differences observed in prevalence and diversity
of parasite species between packs, geographic populations and seasons, but overall a fairly
consistent parasite community composition existed. Significant differences in parasite
prevalence, diversity and infracommunity composition were observed between packs in
Zambia. This difference is likely to be a consequence of the social aspects of packs, such
as close physical contact and ingestion of the same prey items which will result in minimal
variation of parasite fauna within packs. Differences between packs however, will be
maximised even if these variations arise from chance (stochastic) events, rather than
underlying differences in animals or environment. At the population level the composition
of parasite infracommunity did not differ significantly between dogs from Zambia,
Namibia and Zimbabwe. That is, the same types of parasite species were observed in all
wild populations. There was however, a greater parasite load found in populations from
Zambia and Zimbabwe than in the Namibian population. This may be a reflection of
Chapter 3 – Diversity and prevalence of…..
69
climate differences among geographic areas as Zambia and Zimbabwe have similar
climates, whilst the study site located in Namibia is dryer with a desert-like environment
outside the wet season.
Seasonal factors did appear to have an effect on parasite composition and load. The
parasite composition of populations in the wet season displayed a greater abundance of
Ancylostoma spp. and taeniid spp. whilst populations in the dry season had a greater
abundance of Sarcocystis spp. and coccidians. Moist conditions are favourable for the
transmission of Ancylostoma spp. as it is beneficial for the survival of the infective larval
stage hence, transmission rates between hosts are increased, explaining the higher
abundance observed in the wet season. Whilst taeniid ova are extremely resilient to the
environment, prolonged high temperature can reduce survivability and therefore
transmission rates would be reduced in a hot, dry environment and increased in a cool,
moist environment (Lawson and Gemmell, 1983).
Sex or age of the animal appeared not to have any effect on parasite load, parasite
composition or general prevalence of any parasite species. The result for age was
surprising as young animals are often more susceptible and therefore exhibit higher
parasite loads (Bowman et al., 2003). This result may be a reflection of insufficient
sampling of young animals, as samples were difficult to obtain from painted dog pups
which remain at the den site for the first three months. Similar results have been reported,
however, in prevalence studies on other species of wildlife (Muller-Graf et al., 1999; Bjork
et al., 2000; Feliu et al., 2001). In particular, a study on lions in Tanzania infected with
Spirometra spp. found no relationship between sex or age and the mean number of parasite
Chapter 3 – Diversity and prevalence of…..
70
species, although there was geographic variation (Muller-Graf et al., 1999). Additionally,
studies on trematodes and their hedgehog host (Erinaceus europaeus) found no significant
differences in intensities between host sex or age, but again environmental factors such as
season have been shown to be significant (Feliu et al., 2001).
Aggregation of parasites within hosts was evident for all parasite species tested within this
study. Aggregation has been commonly seen in wildlife populations, including painted dog
competitor species such as African lion and spotted hyaena (Muller-Graf, 1995; Shaw et
al., 1995; Engh et al., 2003). The aggregation of parasites within individual hosts can be
due to several factors such as difference in prior history of exposure (young animals with
undeveloped immune systems); difference in susceptibilities to pathogens,
(immunocompromised animal); or simply chance events of infection (Holt and Boulinier,
2005). Aggregation may well be beneficial to the host population as it is thought to
stabilize the host-parasite dynamics (Holt and Boulinier, 2005).
3.4.3 Parasites of wild and captive populations
In all captive populations the diversity and prevalence of parasites was much reduced
compared to wild populations. This was perhaps expected as captive facilities actively
reduce parasitism through modification of diet (a lack of wild prey) and regular treatment
with anthelmintics. The level of difference, however, was quite marked, with animals in
captive facilities virtually parasite-free. This could be of significant consequence for
animals marked for reintroduction programs as they may have insufficient immunity to
withstand the challenge of a ‘natural’ parasite load in the wild. For example, dogs with
Chapter 3 – Diversity and prevalence of…..
71
prior exposure to Ancylostoma spp. are able to build a protective immunity against later
potentially pathogenic burdens, whereas immunologically naïve animals are highly
susceptible to clinical disease (Carroll and Grove, 1985). In the long term, populations
which remain parasite-free over several generations may exhibit an overall reduction in
genetic diversity, in particular in the major histocompatibility complex (MHC) which plays
an important role within the immune system. Studies have found parasite infections have a
selective force on MHC diversity within the host, subsequently increasing diversity of this
important region of the genome (Paterson et al., 1998; Wegner et al., 2003; Gouy de
Bellocq et al., 2008). An increased polymorphism of the MHC may ultimately increase the
ability of the host to mount adequate immune responses to future parasitic infections and is
therefore an important consideration in captive breeding populations.
3.4.4 Conclusions
In summary, this study has obtained comprehensive data on the prevalence and diversity of
gastrointestinal parasites within the painted dog. Several parasites have been reported for
the first time which demonstrates the paucity of information available for this endangered
carnivore. Studies such as this are important to provide a detailed baseline from which
future conservation programs may benefit. Identifying any departures from the ‘normal’
levels of parasitism may indicate threatening processes at play. This could then allow
predictions and subsequent preventions for emerging diseases, as well as providing
guidance for parasite control in captive breeding populations.
Chapter 4 – Molecular epidemiology of…..
72
Chapter 4
Molecular epidemiology of Giardia duodenalis in an endangered carnivore – the African painted dog
A form of this chapter has been published as:
A. Ash, A. Lymbery, J. Lemon, S. Vitali and R.C.A. Thompson (2010), Molecular
epidemiology of Giardia duodenalis in an endangered carnivore – The African painted
dog. Veterinary Parasitology, 174, 206-212.
Chapter 4 – Molecular epidemiology of…..
73
4.1 Introduction
The impact that parasites and other infectious agents have on wildlife has been
increasingly recognized within conservation programs. Stressors such as human
encroachment and habitat destruction are altering the incidence and effect that these
pathogens have on wildlife populations, especially those endangered and under stress
(McCallum and Dobson, 1995; McCallum and Dobson, 2002; Wyatt et al., 2008; Smith et
al., 2009a; Smith et al., 2009b). Habitat destruction results in reduced species ranges and
increased interactions between populations, which in turn raises the risk of disease
transmission between these populations (Scott, 1988; Lyles and Dobson, 1993). Perhaps of
greater significance is human encroachment and the resultant increased interaction of
humans and their domestic animals with co-habiting wildlife. Approximately 80% of
domestic animal pathogens can infect wildlife (Cleaveland et al., 2001) so the risk of
disease spillover into wild populations is potentially great.
Parasite species previously observed in the African painted dog have included the
macroparasites Taenia sp., Ancylostoma caninum, Dipetalonema reconditum and Toxocara
sp. (van Heerden, 1986; van Heerden et al., 1995), and protozoan parasites Babesia canis,
Hepatozoon sp. and Sarcocystis sp. (Colly and Nesbit, 1992; Bwangamoi et al., 1993;
Peirce et al., 1995; Penzhorn, 2006). To date, Giardia have not been recorded in the
African painted dog.
Giardia duodenalis (syn G. intestinalis; G. enterica) is a ubiquitous protozoan parasite
found in a wide range of animals which can cause diarrhoea and ill thrift in a wide range of
host species (Farthing et al., 1986; Thompson, 2004). Molecular characterisation of
Chapter 4 – Molecular epidemiology of…..
74
Giardia duodenalis isolates has identified seven genetically distinct genotypes which
appear to be host specific (Thompson, 2000; Monis et al., 2009). These genotypes have
been named assemblages A through to G. Of interest to this study are Assemblages C and
D which are specific to dogs and Assemblages A and B which affect humans, but are also
found in a variety of other mammals. Assemblages A and B are thus of particular
significance as they are considered potential zoonotic agents. For this reason, there is an
emerging interest in domestic animals and wildlife as possible reservoirs for this parasite.
There have been many published studies of Giardia duodenalis in domestic dogs but
relatively few for wild canids, reflecting the paucity of parasitological studies in wildlife
(Applebee et al., 2005; Thompson et al., 2010).
Domestic dogs are often infected with G. duodenalis assemblages C and D, but
assemblages A and B are also common (van Keulen et al., 2002; Traub et al., 2004a;
Ipankaew et al., 2007; Leonhard et al., 2007; Covacin et al., 2010). Studies of wildlife
species have also observed infections with assemblages A and B and these have raised
questions on the transmission dynamics of this parasite (Graczyk et al., 2002; Fayer et al.,
2006; Thompson et al., 2009). Zoonotic transfer has been suggested between dogs and
humans living in close conditions (Traub et al., 2004a; Lalle et al., 2005; Ipankaew et al.,
2007; Pelayo et al., 2008; Winkorth et al., 2008). However, the total risk appears to be low
(Hopkins et al., 1997; Berrilli et al., 2004). Alternatively, anthropozoonotic transfer has
been suggested, whereby humans may infect other animals, particularly wildlife (Graczyk
et al., 2002; Applebee et al., 2005; Caccio et al., 2005). Overall the transmission dynamics
and subsequent risks to human health or wildlife are not well understood (Caccio et al.,
2005).
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The aim of this study was to examine wild and captive populations of the African painted
dog for the presence of Giardia species, and to genetically characterise any isolates
obtained from these populations using three loci, 18S rRNA, β-giardin and the glutamate
dehydrogenase gene. This will enable identification of Giardia duodenalis at the
assemblage and sub-assemblage levels and subsequently any health risk this parasite may
pose within wild and captive environments of this endangered carnivore.
4.2 Materials and methods
4.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia
during three field trips conducted in 2007, 2008 and 2009. In most cases these samples
were collected within moments of being deposited. The captive samples came from a
population in a zoo in Australia (n = 17) which was also sampled in 2007, 2008 and 2009.
Additionally, two human faecal samples were obtained from zoo keepers working with the
captive population, which had been approved by Murdoch University’s Human Research
Ethics Committee. All samples were given a consistency score of 1 to 5 with 1 being firm
and 5 being liquid. See Chapter 2 for a full description of sample collection methods.
4.2.2 Parasitological techniques
Refer to Chapter 2 for a full description of microscopy methods used. All parasite ova and
cysts observed were recorded, although only data for Giardia are reported here. All
samples were then analysed using PCR protocols specific for Giardia, as described below.
Chapter 4 – Molecular epidemiology of…..
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See Table 4.1 for samples which tested positive for Giardia through microscopy and/or
with PCR amplification.
4.2.3 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted. The
remaining solid matter was used for DNA extraction using the Maxwell® 16 Instrument
(Promega, Madison, USA) as per manufacturer’s instruction. In an attempt to reduce the
impact of inhibitors in carnivore faecal matter, the final elution was diluted to a 5:1 ratio
with nuclease free water.
4.2.4 Amplification of 18S rRNA locus
A nested PCR was used for amplification of a 130 bp product of the 18S rRNA locus. The
primary reaction utilized the primers RH11 and RH4 (Hopkins et al., 1997) and in the
nested reaction primers GiarF and GiarR (Read et al., 2004) were used. The PCR reaction
was performed in 25 μl volumes consisting of 1 µl of extracted DNA, 2.0 mM MgCl2, 1 x
reaction buffer (20 mM Tris-HCL, pH 8.5 at 25 C, 50 mM KCl), 200 µM of each dNTP,
10 ρmol of each primer, 0.5 units of TAQ-Ti DNA polymerase (Fisher Biotec, Perth
Australia), and H2O. DMSO 5% was added to the primary round and 0.5 µl BSA (10
mg/mL) was added to the nested round. Amplification conditions were modified from
Hopkins (1997) and are as follows: the primary reaction was initiated with a denaturing
step of 96 °C for 5 min, then 35 cycles of 96 °C for 45 s, 58 °C for 30 s and 72 °C for 45 s,
Chapter 4 – Molecular epidemiology of…..
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followed by a final extension of 72 °C for 7 min. The nested reaction was altered by a
decrease in annealing temperature to 55 °C.
The PCR product was purified using a Wizard SV gel and PCR Clean-up system
(Promega, Madison, USA) after the manufacturer’s instructions, except the final elution
was reduced to 20 µl from 50 µl. Sequence reactions were performed using the Big Dye
Terminator Version 3.1 cycle sequencing kit (Applied Biosystems) according to the
manufacturer’s instructions. PCR products were sequenced in the reverse direction only
(GiarR), as initial sequencing of forward reactions was unsuccessful in this study as also
seen in others (Leonard et al., 2007, Palmer et al., 2008). Reactions were electrophoresed
on an ABI 3730 48 capillary machine. Assemblages were identified via single nucleotide
polymorphisms (SNP’s) within the 130 bp sequence as previously described by Hopkins et
al. (1997).
4.2.5 Amplification of β-giardin locus
A nested PCR was used for amplification of a 492 bp product of the β-giardin gene. The
primary reaction utilized the primers G7 and G759 (Caccio et al., 2002) and in the nested
reaction primers as described by Lalle (2005) were used. The PCR reaction was performed
in 25 μl volumes consisting of 1 µl of extracted DNA, 2.0 mM MgCl2, 1 x reaction buffer
(67 mM Tris-HCl, 16.6 mM (NH4)2SO4, 0.45% Triton X-100, 0.2 mg/ml gelatin), 200 µM
of each dNTP, 10 ρmol of each primer, 0.5 units of Tth Plus DNA polymerase (Fisher
Biotec, Perth Australia), and H2O. The primary reaction was initiated with a denaturing
step of 95 °C for 5 min, then 40 cycles of 95 °C for 30 s, 65 °C for 30 s and 72 °C for 60 s,
Chapter 4 – Molecular epidemiology of…..
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followed by a final extension of 72 °C for 7 min. The nested reaction was altered by a
decrease in annealing temperature to 55 °C and 35 cycles. The PCR product was purified
and sequenced as described above for the 18S rRNA locus. Assemblages were identified
via SNP’s within the 292 bp sequence when compared with reference sequences
AY072723, AY072727, AY072726, AY072725 and AY45646 (Caccio et al., 2002, Lalle,
2005).
4.2.6 Amplification of the glutamate dehydrogenase locus
A semi-nested PCR was used for amplification of a 432 bp product of the glutamate
dehydrogenase (gdh) gene. The primary reaction utilized the primers GDHeF and GDHiR
with GDHeR and GDHiR in the semi-nested reaction as described by Read et al. (2004).
The PCR reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA,
3.0 mM MgCl2, 1 x reaction buffer (67 mM Tris-HCl, 16.6 mM (NH4)2SO4, 0.45% Triton
X-100, 0.2 mg/ml gelatin), 200 µM of each dNTP, 10 ρmol of each primer, 0.5 units of Tth
Plus DNA polymerase (Fisher Biotec, Perth Australia), and H2O. DMSO 5% was added to
the primary reaction only. Cycling conditions for both reactions were denatured at 94 °C
for 5 min, then 45 cycles of 94 °C for 30 s, 60 °C for 30 s and 72 °C for 1 min, followed by
a final extension of 72 °C for 4 min. The PCR product was purified, sequenced and
analysed as previously described for the 18S rRNA locus. Assemblages were identified via
SNP’s within the 432 bp sequence when compared with reference sequences AY178735,
AY178737, AF069059, AY178739, L40508 and AY178738 (Monis et al., 1995; Monis et
al., 1999).
Chapter 4 – Molecular epidemiology of…..
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4.2.7 Data analysis
Of the 17 samples found positive with microscopy 12 were amplified with PCR along with
27 found negative with microscopy. Prevalence of infection was expressed as percentage
of positive samples found either by microscopy or PCR, with 95% confidence intervals
calculated assuming a binomial distribution, using the software Quantitative Parasitology
3.0 (Rozsa et al., 2000). Faecal consistency scores were compared between dogs testing
positive or negative using a Wilcoxon rank sum test. Differences in prevalence between
populations were tested using the Fisher’s exact test. To compare prevalences between
wild and captive populations, data from year one (2007) of the captive population was
tested against the total individual animals sampled from the wild. Sampling of the captive
population was duplicated each year, but within wild populations animals were sampled
only once as it was found that the composition of packs altered significantly from season to
season, with many deaths recorded and therefore duplicate sampling was extremely rare.
Differences in prevalence of infection among years in the captive population were tested
by a Cochran 2 test, with individual dogs as the blocking factor.
Genotypic information was obtained using the 18S rRNA locus. The multicopy nature and
strong sequence conservation of 18S rRNA provide the sensitivity and specificity required
to determine basic assemblage information (Weilinga and Thompson, 2007). However, to
obtain sub-assemblage information the loci β-giardin and gdh loci were used, as has been
done in many other studies (Abe et al., 2003; Read et al., 2004; Traub et al., 2004a; Lalle
et al., 2005; Leonhard et al., 2007; Palmer et al., 2008). Resultant nucleotide sequences
were compared with published sequences on NCBI. Sequences were aligned against
reference sequences for β-giardin and gdh loci using the sequence alignment program
Chapter 4 – Molecular epidemiology of…..
80
Sequencher™ 4.8 (Gene Codes Corporation, Ann Arbor, USA), allowing assemblage and
sub-assemblage assignment.
4.3. Results
4.3.1 Prevalence of infection
Table 4.1 shows the prevalence of infection with Giardia spp. within the two wild
populations and one captive population of painted dogs. Prevalence of infection with
Giardia did not differ significantly between the two wild populations (P=1.00), but was
significantly greater in the captive population than in either wild population (P=0.03 for
comparison of captive and Zambian populations; P=0.02 for comparison of captive and
Namibian populations). Over all populations, there was no significant difference in faecal
consistency scores between infected (mean score = 2.4 ± SE 0.19) and uninfected (2.3 ±
0.13) dogs (P = 0.78), with only three (n=87) samples presenting with diarrhoea (i.e.
consistency score of 4 or 5).
Table 4.1 Prevalence of Giardia duodenalis (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild populations of the African
painted dog.
Captive
(n=16)
Wild - Zambia
(n=43)
Wild - Namibia
(n=28)
Wild-Total
(n=71)
Cap vs Wild
P value
62%
(37-82%)
28%
(16-43%)
25%
(12-44%)
27%
(17-38%)
0.009
Chapter 4 – Molecular epidemiology of…..
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4.3.2 Molecular characterization of Giardia duodenalis isolates
All samples were initially screened at the 18S rRNA locus and identified as Giardia
duodenalis. Samples successfully amplified at the 18S locus and/or found to be positive
with microscopy were also amplified at the β-giardin and gdh loci. Within the captive
population, isolates from 16 individual animals were successfully amplified at one, two or
three loci. Amplification was successful for isolates from 14 animals at the 18S rRNA
locus, three at β-giardin and six at gdh. Within the wild population, isolates from 14
individual animals were amplified: 13 at 18S rDNA, seven at β-giardin and one at gdh
(Table 4.2). Isolates from both captive and wild populations displayed variation in
assemblage and sub-assemblage type depending on the locus used (Table 4.2).
Chapter 4 – Molecular epidemiology of…..
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Table 4.2 Genotypic characterisation of Giardia duodenalis isolates from individual
African painted dogs at the18S rRNA, β -giardin and gdh loci. * Wild animals over 2yrs of
age were allocated as Adult (A).
Captive population (n=16) Wild population (n=14)
ID No Sex Age 18S β-g gdh ID No Sex Age* 18S β-g gdh
C1 M 1 A/B - - W1 F A A - -
C2 M 1 A/B - - W2 M 1 B A
C3 M 3 B - A2 W3 ? ? B BIII -
C4 M 1 B BIII/BIV - W4 F A B - -
C5 M 2 B - BIV W5 M A A/B A2 -
C6 M 2 B - - W6 F A A/D A2 -
C7 M 2 A/B - - W7 M A B A2 -
C8 M 3 B/C - - W8 M A A/B/C - -
C9 M 7 B - - W9 ? A B - -
C10 M 9 B - - W10 ? ? A/B - -
C11 M 3 - - BIV W11 ? ? A/B - -
C12 F 2 - BIII/BIV BIV W12 ? A - A2 -
C13 F 1 B - - W13 M A C/D - -
C14 F 4 B BIII/BIV A2 W14 F A A/B/C BIII BIV
C15 F 4 B - D
C16 F 8 B - -
Assemblage information obtained from the 18S rRNA gene showed a dominant proportion
of samples in the captive population to be assemblage B (86%) with mixed assemblages
A/B and B/C/D both being 7%. Within the wild population assemblage B was also
dominant with 38% of isolates however, greater variability was seen in the remaining
isolates with several mixed assemblages.
Chapter 4 – Molecular epidemiology of…..
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Longitudinal data were obtained from the captive population as sampling was conducted
every year for three years (Table 4.3). Giardia duodenalis was observed in each year, with
prevalences ranging between 50% and 69%. All animals tested positive at least once
throughout the sampling period and there was no significant difference in prevalence
among years (2 = 0.19, P = 0.16). Assemblages A and B were seen in high proportions in
each year.
Table 4.3 Prevalence (with 95% confidence intervals in parentheses) and genotypic
characterisation of Giardia isolates obtained in a captive population of African painted
dogs over a three year period.
Sample year Prevalence 18S rRNA β-giardin gdh
2007
n=16
62%
(37-82%)
B=5
A/B=3
BIII/BIV=1 BIV=1
2008
n=14
50%
(24-76%)
B=5
B/C/D=1
BIII=1
BIII/BIV=1
2009
n=13
69%
(41-88%)
B=6 BIV=1 AII=2
BIII=1 BIV=1
A/B/D=1
Isolates obtained from the two zookeepers were also amplified at the 18S rDNA and β-
giardin loci. Sequencing of the 18S rRNA gene revealed assemblage B and BIII/BIV at the
β-giardin locus for both isolates.
Chapter 4 – Molecular epidemiology of…..
84
4.4. Discussion
This study is the first to identify Giardia duodenalis in the African painted dog. Previous
parasitological studies on this animal have not found this protozoan (van Heerden, 1986;
Colly and Nesbit, 1992; Peirce et al., 1995; van Heerden et al., 1995; Penzhorn, 2006).
The prevalence of G. duodenalis in the wild, 28% in the Zambian population and 25% in
the Namibian population, was similar to other reports in wild canids, e.g. 12.5-32% in
coyotes (Gompper and Williams, 1998; Trout et al., 2006; Thompson et al., 2009), and
46% in wolves (Klock et al., 2005). The greater prevalence found in this study in the
captive population (62.5%) is most likely indicative of their captive environment. Animals
are housed over long periods in the same area, allowing environmental build up and
continued cycling of this protozoan within the population. This effect is reduced in wild
populations as they are extremely nomadic.
This study was not successful in amplifying all isolates at all loci. Previous studies have
also reported lower than expected amplification of Giardia DNA in dogs (Read et al.,
2004; Traub et al., 2004a; Robertson et al., 2006; Leonhard et al., 2007; Caccio and Ryan,
2008; Palmer et al., 2008). The inability to amplify at all loci may be attributed to several
factors. First, β-giardin and gdh loci require high cyst numbers for amplification success
(Castro-Hermida et al., 2007). In addition, faecal samples from carnivores in general have
low PCR success, due to the presence of inhibitors (Kohn and Wayne, 1997; Piggott and
Taylor, 2003; Covacin et al., 2010). Finally, the majority of samples in this study were not
fresh but placed in a fixative, which was necessary to preserve DNA and to comply with
quarantine restrictions for sample importation, but probably reduced the success of DNA
Chapter 4 – Molecular epidemiology of…..
85
amplification due to degradation. Even when amplification was successful, some isolates
showed differences in assemblage and sub-assemblage typing depending on the locus used.
This has also been found in previous studies and may be due to meiotic recombination or
preferential amplification of one assemblage over another in mixed infections (Caccio et
al., 2005; Cooper et al., 2007; Teodorovic et al., 2007; Caccio and Ryan, 2008).
Despite the difficulties mentioned above, it was possible to obtain some assemblage and
sub-assemblage information for both wild and captive populations of the African painted
dog. Genotypic information did not reveal any novel genotypes, but the zoonotic
assemblages B and to a lesser degree A were prevalent within both populations. The
dominance of these zoonotic assemblages was surprising especially as the dog assemblages
C and D were rarely seen. Assemblages A and B have been reported in studies on domestic
dogs, coyotes and wolves but the dog assemblages have also been reported at similar
prevalences (Table 4.4). The lack of assemblages C and D seen in both wild and captive
populations of this study perhaps indicate that the African painted dog is not as susceptible
for this genotype as members of the genus Canis. Interestingly, assemblage A has been the
dominant zoonotic genotype reported in the literature in studies of both wild canids and
domestic dogs, as opposed to this study, where assemblage B was the dominant genotype
(Table 4.4).
Chapter 4 – Molecular epidemiology of…..
86
Table 4.4 Assemblages of Giardia duodenalis observed in both wild canids and domestic
dogs noted in the literature and this study. Number of times reported in literature is
presented as (r=).
Host Assemblage Reference
Canis
familiaris
A (r=11)
B (r=3)
(van Keulen et al., 2002; Berrilli et al., 2004; Read et al., 2004; Traub et al.,
2004a; Itagaki et al., 2005; Lalle et al., 2005; Ipankaew et al., 2007; Leonhard
et al., 2007; Palmer et al., 2008; Covacin et al., 2010; Marangi et al., 2010)
C/ D (r=11) (Monis et al., 1998; Berrilli et al., 2004; Itagaki et al., 2005; Lalle et al., 2005;
Ipankaew et al., 2007; Leonhard et al., 2007; Souza et al., 2007; Palmer et al.,
2008)
Canis latrans
and
Canis lupus
A (r=3)
B (r=1)
C /D (r=3)
(Gompper et al., 2003; Klock et al., 2005; Trout et al., 2006; Thompson et al.,
2009)
Lycaon pictus A
B
Present study
As noted in other wildlife studies, the presence of the zoonotic assemblages found in the
African painted dog raises the question of their potential to act as reservoirs for human
infection (Graczyk et al., 2002; Trout et al., 2006; Thompson et al., 2009). The answer can
perhaps be explained by their ecology and environment. Close interaction between dogs
and humans living in rural communities in India has shown evidence of zoonotic
transmission of Giardia (Traub et al., 2004a) and indeed this kind of transmission could
well be possible within captive populations of the African painted dogs. The zoo keepers in
our study had direct contact with the African painted dogs’ confined environment and were
at risk of exposure through regular cleaning of water features and removing excrement
Chapter 4 – Molecular epidemiology of…..
87
from the enclosure. Isolates from the two keepers typed to the same sub-assemblage as one
of the captive animals in their care, suggesting that zoonotic transmission may have
occurred. Evidence for zoonotic transmission within the zoo environment has also been
observed for another protozoan, Blastocystis sp. whereby keepers and animals were found
to harbour the same genetic sub-type of this parasite (Parkar et al., 2010).
In the wild, however, human contact with the African painted dog would be minimal. They
are not companion animals and have never been domesticated. Due to their nomadic nature
they will roam outside national parks and move through human settlements, although they
actively avoid human contact, making zoonotic transfer unlikely (Creel and Creel, 2002).
However, there is a constant stream of tourists and locals into the national parks and as
suggested by Graczyk et al. (2002) studying gorillas in Uganda, indiscriminate defecation
by humans could be a source of Giardia infection. Other evidence for anthropozoonotic
transmission has been seen between humans and beavers, where humans have been
implicated in introducing Giardia to beavers through sewage runoff upstream from the
beaver colony (Bemrick and Erlandsen, 1988; Fayer et al., 2006).
Whilst the transmission of Giardia duodenalis from humans to African painted dogs
remains speculative, it appears that once established within these packs infection is
maintained by dog to dog transmission. They are very social animals and physical contact
is common in all aspects of pack life, providing ample opportunity for transmission to
occur (Woodroffe et al., 1997; Creel and Creel, 2002). This was evident in the captive
population as each individual animal displayed an infection with G. duodenalis at some
point over the three year study period. As previously mentioned, prevalence was far lower
Chapter 4 – Molecular epidemiology of…..
88
in the wild populations and distribution among packs was not even. G. duodenalis was
observed in several individuals in the same pack and in none in other packs, again
suggesting that once the parasite is introduced into a pack, animal to animal transmission
occurs.
The pathogenesis of Giardia spp. to the host is complicated as many infected hosts can be
asymptomatic while others display severe diarrhoea (Eckmann, 2003). In this study, only
three of the 85 faecal samples positive for G. duodenalis showed signs of diarrhoea,
suggesting that parasitic infection in these animals was generally asymptomatic. Perhaps of
more importance than clinical symptoms are the potential subclinical effects. Infections
with Giardia spp. have been related to growth retardation and malabsorption in children,
particularly those with poor nutrition (Astiazaran-Garcia et al., 2000; Berkman et al.,
2002). With respect to African painted dogs, which often have concurrent enteric
infections (see Chapter 3), subclinical impacts of G. duodenalis could be of great
importance, particularly as pack sizes decrease and hunting efficacy declines (Creel and
Creel, 1995; Courchamp et al., 2002).
Ultimately, the transmission dynamics of G. duodenalis within the African painted dog
remains unclear. While this species could act as a reservoir for zoonotic infections, the lack
of direct human contact in the wild make this unlikely. However, increased human activity
into their natural environment clearly has the potential to increase the prevalence of G.
duodenalis infections in the African painted dog. With other pressures this could
potentially be an emerging disease, which will require monitoring in the future. This
dynamic, however, is altered within captive populations. Due to the necessary interaction
Chapter 4 – Molecular epidemiology of…..
89
between humans and their captive charges in this environment, the risk of zoonotic transfer
is high and should be a consideration in future management protocols.
4.4.1 Conclusions
In summary, the prevalence of G. duodenalis observed in this study indicates that this
parasite is an important part of the parasite fauna of both wild and captive populations of
the African painted dog. Molecular techniques have demonstrated that both wild and
captive populations are predominantly infected with the zoonotic assemblages of G.
duodenalis, and therefore pose a potential zoonotic risk for zoo keepers and surrounding
communities in the natural environment. The subclinical effects of infection are unknown,
but are potentially detrimental to small packs with limited prey capture success and
subsequent poor nutrition. This is the first report of G. duodenalis within the painted dog
and may indicate an emerging disease with possible zoonotic/anthropozoonotic
transmission modes. This highlights the need for continued research to be conducted on
wildlife and their surrounding influences to ascertain more precisely the nature of any
threats to the charismatic but endangered African painted dog.
Chapter 5 – Hookworm species of…..
90
Chapter 5
Hookworm species of the African painted dog and the significance of infection
Chapter 5 – Hookworm species of…..
91
5.1 Introduction
The family Ancylostomatidae contains parasitic nematodes which infect the small
intestine of a wide range of mammalian hosts. These nematodes have a large buccal
cavity, usually armed with teeth, at the anterior end which assists in attachment to the
hosts’ intestinal wall. The anterior end is often ‘hooked’ in appearance, giving rise to
the nomenclature of Ancylostoma with ancyl being Greek for ‘hook’ and stoma for
‘mouth’ (Dubini, 1843).
Infection of the host can occur either through direct ingestion or skin penetration of
infective larvae (L3) (Looss, 1898; Fulleborn, 1914) (Figure 5.1). Larvae which
penetrate the skin usually undergo a tracheal migration where larvae migrate to the
lungs, are ‘coughed’ into the trachea, swallowed and taken through the digestive system
where eventually they reach the small intestine to then attach, feed and reproduce
(Looss, 1898; Bowman et al., 2003). Alternatively L3 may undergo somatic migration
whereby larvae move through the host tissue and localize in the skeletal muscle and
enter into a hypobiotic (dormant) state. These dormant larvae are able to reactivate,
move into the gut and develop into reproducing adults when optimal transmission
conditions occur (Loukas and Provic, 2001). An example of this is when a canid host
gives birth. Encysted larvae are reactivated towards the end of the pregnancy and are
ready to produce large quantities of eggs for quick transmission to the newly born pups
(Bowman et al., 2003). Pups can also be infected through transmammary transmission,
which occurs when larvae emerging from hypobiosis migrate to the mammary glands
and pass through to nursing pups in the dam’s milk (Figure 5.1). Both routes of
infection result in large parasite loads within these young hosts often leading to severe
anaemia as a direct result of the feeding activities of these parasites (Kalkofen, 1970).
Canid hookworm species are important concerns for both animal and human health as
Chapter 5 – Hookworm species of…..
92
besides the ability to cause clinical disease in canids, these hookworms also have the
potential to infect humans.
Figure 5.1 Depiction of the lifecycle of Ancylostoma caninum in domestic dogs
adapted from www.Apaws.org.
.
5.1.1 Hookworm in the canid host
The most widespread species of hookworm infecting canids is Ancylostoma caninum
which has a cosmopolitan distribution (Miller, 1971). Other hookworm species
commonly infecting canids include A. braziliense, A. ceylanicum and Uncinaria
stenocephala all of which have a more restricted distribution. U. stenocephala is
commonly observed in the cooler climates of Europe, North America and Australia,
while A. braziliense and A. ceylanicum are observed in warmer tropical and sub-
tropical regions (Levine, 1968; Provic, 1998; Beveridge, 2002). A. braziliense is quite
widely distributed in these regions but to date A. ceylanicum has only been reported in
Chapter 5 – Hookworm species of…..
93
Southeast Asia, India and more recently Australia (Yoshida et al., 1973; Choo et al.,
2000; Loukas and Provic, 2001; Traub et al., 2004b; Palmer et al., 2007).
Within the canid host, hookworm infections can range from being largely
asymptomatic to severely pathogenic depending on the species of hookworm,
magnitude of infection and the susceptibility of the host (Bowman et al., 2003). A.
caninum infections are often more pathogenic to the canid host due to a greater rate of
blood loss than seen with A. ceylanicum, A. braziliense or U. stenocephala infections
(Miller, 1966; Areekul et al., 1975; Bowman et al., 2003). However, heavy infections
of most hookworm species can lead to clinical disease (Carroll and Grove, 1984). The
magnitude of infection depends on the level of exposure to infective larvae in the
environment, which in turn is dependent on proximity of other infected hosts and
suitability of the environment for the development and survival of the L3.
Host susceptibility is often dependent on age and immune function with young animals
and older immunocompromised animals most at risk, with even light infections capable
of causing illness and death. However, hosts with prior exposure or premunition are
often asymptomatic. Carroll and Grove (1985) demonstrated this ability for acquired
resistance to A. ceylanicum in experimental trials on dogs. They found that dogs
currently infected with small numbers of hookworms were considerably resistant to a
challenge infection of a large inoculum of infective larvae, while dogs previously
uninfected with hookworm developed marked anaemia when inoculated.
5.1.2 The zoonotic potential of canid hookworm species
Canid hookworm species have zoonotic potential and are associated with a variety of
diseases in humans (Carroll and Grove, 1986; Chaudhry and Longworth, 1989; Croese
Chapter 5 – Hookworm species of…..
94
et al., 1994). All canid hookworm species are capable of causing cutaneous larval
migrans (CLM), also known as ‘creeping eruptions’ (Kirby-Smith, 1926; Carroll and
Grove, 1986; Jelinek et al., 1994). CLM is a pruritic skin disease which is the result of
infective hookworm larvae penetrating and migrating through the skin (Jelinek et al.,
1994). Cases of CLM are most often described in hot climates including SE Asia,
Africa and Latin America with A. braziliense the most common etiological agent
involved (Chaudhry and Longworth, 1989). A. caninum has been shown to sometimes
migrate further than the skin reaching the human gut where it can cause eosinophilic
enteritis; however evidence of patency has not yet been observed (Croese et al., 1994).
A. ceylanicum is the only hookworm of dogs that is capable of producing patent
infections in the human host, with patients experiencing intermittent abdominal
discomfort throughout the period of infection (Carroll and Grove, 1986).
5.1.3 Hookworm in the African painted dog and other carnivores in Africa
Reports of hookworm within African animals have mainly been from domestic dogs
and cats with A. caninum most common in dogs and A. tubaeforme in cats (Baker et al.,
1989; Minnaar and Krecek, 2001; Minnaar et al., 2002). A. braziliense was also
reported in these studies but at slightly lower prevalences. Baker et al. (1989) reported
parasitological studies during autopsies on 1,500 stray cats and identified A. ceylanicum
at a prevalence of 1.4%. To date this is the only report of this Ancylostoma species in
Africa in either human or animal populations. Reports of hookworm species in native
African carnivores are less common, however A. caninum and A. braziliense have been
identified in cheetah (Acinonyx jubatus), leopard (Panthera pardus) and jackal (Canis
spp.) (Round, 1968). A. ceylanicum was also reported in an African civet (Viverra
civetta), although during this time A. ceylanicum and A. braziliense were considered
Chapter 5 – Hookworm species of…..
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synonymous and were not officially differentiated until 1951 (Bioca, 1951; Round,
1968). With this redescription it has been suggested that many old records are in doubt,
therefore this identification is also questionable (Dunn, 1969). The only reports of
hookworm in the African painted dog have been from van Heerden et al. (1994, 1996)
who found A. caninum in a captive and wild population in South Africa.
5.1.4 Diagnosing hookworm infections
In the past, studies using microscopy to identify parasite ova have had to presume or
suggest which species of Ancylostoma was the infecting agent based on previous
observations from that host and the known distribution of hookworm species (Engh et
al., 2003; Smith and Kok, 2006). This may have led to erroneous reports as the
identification of Ancylostoma species from parasite ova alone is not possible.
Traditional methods of species identification have involved obtaining adult worms,
usually during necropsy, which in turn required considerable expertise to differentiate.
Historically, misidentifications have been made, particularly between A. ceylanicum
and A. braziliense due to the morphological similarities between the two, creating doubt
on known distributions (Dunn 1969). Recent development of molecular tools to
differentiate hookworm species from faecal samples has been able to alleviate these
diagnostic problems and allow for more accurate species identification and
subsequently more accurate distribution records for parasites (Palmer et al., 2007;
Traub et al., 2008). For example, the distribution of A. ceylanicum was only recently
found to include Australia (Palmer et al., 2007). This range extension was demonstrated
with the use of molecular tools which were able to differentiate between eggs from
different Ancylostoma species from canine faeces (Traub et al., 2004b).
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The primary aim of this study was firstly, to establish the prevalence of Ancylostoma
spp. in captive and wild populations of the African pained dog and secondly, to identify
if species of pathogenic and/or zoonotic importance occur within these populations.
These aims were achieved by obtaining data from three wild and three captive
populations for comparative analysis. Molecular characterisation was conducted to
identify species of Ancylostoma.
5.2 Materials and methods
5.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia
during three field trips conducted between 2007 and 2009. The population within
Zambia was sampled in each of the three years while the population in Namibia was
sampled in two of these years (2008 and 2009). Samples in Zimbabwe had been
collected in 2006 and stored for later analysis. The samples from captive animals were
collected from two zoo populations in Australia (Perth Zoo, Monarto Zoo) and a
rehabilitation facility in South Africa. See Chapter 2 for a full description of sample
collection methods.
5.2.2 Parasitological techniques
Refer to Chapter 2 for a detailed description of microscopy techniques. All parasite ova
and cysts observed were recorded, although only data for Ancylostoma spp. are reported
here. All samples were then analysed using PCR protocols specific for Ancylostoma
spp., as described below.
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5.2.3 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted.
The remaining solid matter was used for DNA extraction using the Maxwell® 16
Instrument (Promega, Madison, USA) as per the manufacturer’s instruction. In an
attempt to reduce the impact of inhibitors in carnivore faecal matter, the final elution
was diluted to a 5:1 ratio with nuclease free water.
5.2.4 Amplification of Ancylostoma spp. isolates at the ITS1 and ITS2 regions
Modifications from Traub et al. (2008) were used for amplification of a 380 bp product
of the ITS1, 58S and ITS2 regions using primers RTHW1F and RTHW1R. The PCR
reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA, 2.5 mM
MgCl2, 1 x reaction buffer (20 mM Tris-HCl, pH 8.5 at 25 °C, 50 mM KCl), 100 µM of
each dNTP, 10 ρmol of each primer, 0.5 units of Tth plus DNA polymerase (Fisher
Biotec, Perth Australia), and H2O. Amplification conditions were as follows: the
primary reaction was initiated with a denaturing step of 95 °C for 5 min, then 40 cycles
of 95 °C for 30 s, 60 °C for 30 s and 72 °C for 30 s, followed by a final extension of 72
°C for 7 min. The PCR product was purified using an Agencourt AMPure XP system
(Beckman Coulter Inc, Brea USA) according to the manufacturer’s instruction.
Sequence reactions were performed using the Big Dye Terminator Version 3.1 cycle
sequencing kit (Applied Biosystems), according to the manufacturer’s instructions.
PCR products were sequenced in both directions. Reactions were electrophoresed on an
ABI 3730 48 capillary machine.
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5.2.5 Data analysis
Prevalences of infection were expressed as a percentage of positive samples found by
microscopy with 95% confidence intervals calculated assuming a binomial distribution,
using the software Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in
prevalence between populations and years were tested using the Fisher’s exact test or
chi-square test. Resultant nucleotide sequences were compared with published
sequences on NCBI GenBank using the basic alignment search tool (BLAST). Further
sequence analysis was conducted using the sequence alignment program Sequencher™
4.8 (Gene Codes Corporation, Ann Arbor, USA). Reference sequences for A. caninum,
A. duodenale and A. braziliense (accession numbers A. caninum DQ438079 and
EU159416, A. duodenale EU344797 and AB501351, A. braziliense DQ438054) were
used in the alignments. The levels of sequence differences (D), based on pairwise
comparisons, were calculated using the formula D = 1 – (M/L), where M is the number
of alignment positions at which the two sequences have a base in common and L is the
total number of positions over which the sequences are compared (Chilton et al., 1997).
The level of sequence difference was expressed as a percentage.
5.3 Results
5.3.1 Prevalence of infection
Table 5.1 shows the prevalence of infection with Ancylostoma spp. within captive and
wild populations. Prevalence of infections did not differ significantly between the three
wild populations (Fisher’s exact tests, Zambia vs. Namibia P=0.4; Zambia vs.
Zimbabwe P=0.14; Namibia vs. Zimbabwe P=0.6). There was a significant difference
in prevalence between wild and captive populations, as Ancylostoma spp. were not
observed in any of the captive populations sampled (Fisher’s exact test, P< 0.0001).
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Table 5.1 Prevalence of Ancylostoma spp. (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild populations of the
African painted dog.
Zimbabwe
(n=12)
Zambia
(n=43)
Namibia
(n=28)
Total wild
(n=83)
Total captive
(n=130)
8 % 32.6% 43% 32.5% 0
(0.4 – 37%) (19 – 48%) (26 – 62%) (23 – 43%)
Data was obtained over three years for the Zambian population and two years for the
Namibian populations. Ancylostoma spp. were observed in each year with prevalences
ranging from 20% to 66.7% (Table 5.2). There were significant differences in
prevalences among years within the Zambian population (χ2 = 6.306, P=0.04) but not
between years in the Namibian population (Fisher’s exact test, P=1.000).
Table 5.2 Prevalence of Ancylostoma spp. observed in the Zambian and Namibian
populations of the African painted dog over a three year period. Sample size (n) and
95% confidence intervals in parentheses.
Population Year
2007 2008 2009
Zambia
66.7% (n=9)
(32 – 90%)
20% (n=20)
(71 – 42%)
28.6% (n=14)
(10 – 57%)
Namibia
42% (n=19)
(22 – 66%)
44% (n=9)
(17 -75%)
-
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5.3.2 Molecular characterisation of Ancylostoma spp. isolates
Of the 27 samples identified positive for Ancylostoma spp. ova by microscopy, a subset
were chosen for molecular characterisation. Four samples were successfully amplified
at the ITS1 and ITS2 regions. A BLAST search on GenBank revealed three isolates
from the Namibian population (N-B08, N-K17 and N-U12) to be Ancylostoma
braziliense and one isolate from the Zambian population (Z-Ka01) was found to have a
similar identity to both Ancylostoma caninum and Ancylostoma duodenale (Table 5.3).
Table 5.3 Genotypic characterisation of Ancylostoma spp. isolates obtained from wild
populations of the African painted dog within Zambia and Namibia. Percentages shown
for matched identities with published sequences in parentheses.
Population Isolate Host Sex Host Age Ancylostoma species
Namibia N-B08 ? ? A. braziliense (100)
Namibia N-K17 ? Adult A. braziliense (100)
Namibia N-U12 ? ? A. braziliense (100)
Zambia Z-Ka01 M Yearling A. caninum (99) A. duodenale
(99)
The isolate Z-Ka01 was aligned against reference sequences of A. caninum (accession
numbers DQ438079 and EU159416) and A. duodenale (accession numbers
AB501351and EU344797). Over a 301 bp region there was one different nucleotide
Chapter 5 – Hookworm species of…..
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difference with A. duodenale and two nucleotide differences with A. caninum (Table
5.4).
Table 5.4 Summary of the nucleotide variations detected between the painted dog
isolate from Zambia (Z-Ka01) and reference sequences for A. caninum and A.
duodenale. Alignment was conducted in Sequencher™ 4.8 and dots indicate identity
with the first sequence.
Ancylostoma isolates Alignment position
324 353 355
A. caninum EU159416 T C C
A. caninum DQ438079 . T .
A. duodenale EU344797 A T T
A. duodenale AB501351 . T T
Z-Ka01 . T T
5.4 Discussion
Ancylostoma spp. were not detected within any of the captive populations of the
African painted dog. This was most likely due to the regular use of anthelmintics in the
captive facilities (see Chapter 2). In comparison, the total prevalence of Ancylostoma
spp. observed in the wild populations of painted dogs in this study was 32.5%. This was
slightly higher than previously reported by van Heerden et al. (1995), (22.4%) but
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varies from studies on competitor species such as hyaena, which reported a prevalence
of 56%, and lion (90%) (Muller-Graf, 1995; Engh et al., 2003). It is not clear whether
the higher prevalences observed in studies of hyaena and lion were due to
environmental conditions or differences among hosts in exposure or resistance to
hookworm infection.
In this study prevalence of infection was not significantly different between African
painted dog populations in different geographic regions, however, within the Zambian
population a significant difference was observed over time. This variation was mainly
due to the higher prevalence observed in 2007, which also had the majority of samples
collected in the wet season. The wet season in these regions provide a moist and warm
environment which are optimal conditions for the transmission and survival of
hookworm larvae and this is the most likely explanation for the observed increased
prevalence in 2007.
The use of molecular tools in this study allowed for species identification of a small
subset of isolates. Using the ITS region of hookworm rDNA it was possible to
distinguish between the main species of canid hookworms (Traub et al., 2004b; Clare e
Silva et al., 2006). A major benefit of using molecular tools is that it avoids the need for
adult worms which are usually only obtained during a necropsy and require substantial
skill to confidently identify (Traub et al., 2004b). This is particularly important when
dealing with endangered wild animals, where the chances of obtaining carcasses for
necropsy is rarely possible. Faecal sampling provides a non-invasive method to obtain
parasitological data, from which molecular tools can then assist in providing species
information.
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The ability to identify the species of hookworm infecting a host population is of
particular significance as pathogenicity and zoonotic potential vary between the
different species. For example, A. caninum poses a greater health risk to the host as it
causes greater blood loss than the other species, whilst A. braziliense commonly causes
CLM in humans and A. ceylanicum can lead to patent infections in man (Miller, 1966;
Carroll and Grove, 1986). Additionally, as correct species identification has been
impossible through egg morphology, the exact geographic distribution for these
hookworm species is not completely mapped, making molecular characterisation an
important tool in achieving this.
Genetic characterisations conducted in this study identified three isolates from the
Namibian population of painted dogs to be A. braziliense. This is the first identification
of this species of hookworm in the painted dog and potentially represents a zoonotic
risk to the surrounding human communities. A previous study on communities situated
near this study population has implicated A. braziliense as a major cause of CLM
commonly seen in hospital patients (Evans et al., 1990). Theoretically, these animals
could be reservoirs for CLM in human communities but the lack of human contact in
the wild would reduce the chance of transmission (see Chapter 4).
A more likely explanation for the CLM seen in human populations would be zoonotic
infection from the large number of domestic dogs living in close contact with these
communities. A. braziliense has been reported in domestic dogs in Africa with
prevalences ranging from 19% to 79% (Pangui and Kaboret, 1993; Minnaar and
Krecek, 2001; Minnaar et al., 2002). Two concurrent studies conducted in different
regions of South Africa found that the prevalence of A. caninum was significantly less
in the study site with the drier climate (27% vs. 88%) whilst A. braziliense had similar
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prevalences in both climates (19%, 20%). The authors therefore suggested that A.
braziliense were more resistant to dry environment than A. caninum (Minnaar and
Krecek, 2001; Minnaar et al., 2002). Conclusive evidence for this is lacking in the
literature but another study on domestic dogs in Dakar, Senegal, which has a semi-arid
climate found A. braziliense at much higher prevalences than A. caninum (79% vs.
17%) (Pangui and Kaboret, 1993). A. braziliense was the only species identified from
Namibia in this study, which is a region that experiences a desert dry environment for
most of the year and a shorter wet season than the other study sites of Zambia and
Zimbabwe.
The single isolate which was sequenced from the Zambian population could not be
conclusively identified as either A. caninum or A. duodenale due to the lack of
polymorphisms within the sequenced region. A. duodenale is known as a human
hookworm but is also found in cats and dogs. This species has not been previously
reported in the African painted dog although it has been reported in the spotted hyaena
in Ethiopia (Graber and Blanc, 1979). A. caninum has been reported in both a captive
and wild population of the African painted dog (van Heerden et al., 1994). However, it
must be noted that the study on the wild population within Kruger National Park
identified A. caninum from one adult worm obtained from one painted dog during
necropsy. It appears that it was then assumed that all Ancylostoma spp. ova observed in
faecal samples of that study were of the same species, which may well have been
inaccurate. Studies have since identified A. braziliense within domestic dog populations
of South Africa, providing evidence that the species exists within the region and is
therefore a possible suspect (Minnaar and Krecek, 2001; Minnaar et al., 2002). As
molecular tools become more widely used these issues may be resolved.
Chapter 5 – Hookworm species of…..
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Pathogenicity of hookworm infection within wild populations of the African painted
dog is unknown (van Heerden et al., 1995). It is likely that some mortality events occur
but identifying these in the wild is hindered by the inability to find dead animals in
what is often inaccessible terrain, combined with the efficiency of scavengers in
cleaning up carcases. Nonetheless, the painted dogs are extremely social animals so the
transmission of hookworm between individuals would be greatly enhanced.
Transmission would be significantly increased during the denning period when
reactivated larvae in the dam increase ova output and pups and pack members are
confined to the den and surrounding areas. It appears the prevalence of hookworm
observed in these wild populations was sustainable as study animals appeared robust
and healthy. This display of health may be the result of acquired immunity by the host
or, as has been previously noted, wild animals tend to manifest few recognizable signs
of disease (Sachs and Sachs, 1968; Young, 1969). This apparent health has been
observed in other wild populations who are host to potentially pathogenic parasites.
Wild populations of zebra are known to harbour a variety of Cyathostomum spp., of
which several species are pathogenic to domestic equines, but the zebra host appears to
display no clinical effects (Roberts et al., 2002). Similarly, populations of wild
ruminants within north America are host to many gastrointestinal strongyle parasites,
many of which are pathogenic to domestic livestock, but again negligible clinical
effects have been in observed in these wild hosts (Hoberg et al., 2001).
The ability for the canid host to acquire a level of immunity to hookworm infections is
an important consideration for captive animal management, especially those involved
in reintroduction programs. The prevalences observed in this study indicate that
hookworm infections are common within wild populations while captive animals have
no or minimal exposure. Therefore, facilities with animals marked for reintroduction
Chapter 5 – Hookworm species of…..
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programs may benefit from maintaining a low level of infection in order for animals to
acquire a level of immunity against species such as hookworm. In addition, exposure to
A. caninum can lead to cross immunity for other hookworm species such as A.
braziliense (Miller, 1967). These factors would then reduce the impact of the
substantial parasite challenge animals will be faced with on release to the natural
environment (Williams et al., 1992; Viggers et al., 1993).
There is a risk involved in maintaining infections with naturally occurring parasites in a
captive environment as the confined conditions can lead to a rapid increase in parasite
numbers. Therefore, adequate monitoring would be required to ensure infection levels
remained low to avoid clinical disease, but the benefits may be worth the extra labour
involved. It should be noted that ancylostomiasis has been implicated in the death of
two captive painted dogs (van Heerden et al., 1994). However, one animal was a pup
and the other was an immunocompromised adult, both of which were particularly
susceptible to hookworm infections. Depending on individual facilities the risk of some
mortality may be acceptable in view of the benefits potentially gained.
5.4.1 Conclusions
In summary, these prevalence data suggest that Ancylostoma species make up an
important part of the parasite fauna of wild populations of the painted dog. Molecular
techniques have been successful in identifying A. braziliense for the first time in this
endangered carnivore and indicate a possible zoonotic risk for the surrounding human
communities. As DNA from only a small subset of samples was successfully amplified
and sequenced, limited information on geographic distribution was obtained. Future
Chapter 5 – Hookworm species of…..
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studies are required to achieve detailed species distribution within endangered
carnivores such as the African painted dog.
Chapter 6 – Detecting Taenia species in…
108
Chapter 6
Detecting Taenia species of the African painted dog
Chapter 6 – Detecting Taenia species in…
109
6.1 Introduction
The cestode family Taeniidae consists of two genera, Taenia Linnaeus, 1758 and
Echinococcus Rudolphi 1801¸ both of which include species of medical and veterinary
significance (Eckert et al., 2001; Hoberg, 2002). These taeniids have a two host lifecycle
based around a carnivorous definitive host and an omnivorous or herbivorous intermediate
host. The adult worm lives in the gut of the definitive host where it produces proglottids
which once mature contain multiple ova. These proglottids and ova are passed out in the
hosts’ faeces and are subsequently ingested by grazing herbivores and omnivores. Once
ingested by the intermediate host the ova develop into a larval stage, or metacestode, which
encysts within the tissues and internal organs of the intermediate host. These metacestodes
are fluid-filled cystic structures which depending on the species develop into cysticerci,
strobilocerci, coenuri or hydatid cysts (Bowman et al., 2003). Cysticerci and strobilocerci
contain one scolex from which one mature tapeworm can develop. Coenuri contain
multiple scolices and hydatid cysts can contain thousands of scolices (protoscolices). The
latter two are usually associated with pathogenic disease in the intermediate host due to the
invasive or space occupying nature of the cysts. The taeniid lifecycle is completed when
these metacestodes are ingested by a carnivorous definitive host (Figure 6.1).
Chapter 6 – Detecting Taenia species in…
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Figure 6.1.The lifecycle of a taeniid species depicting the transmission cycle between
predator (definitive host) and prey (intermediate host).
There are multiple species within both genera of taeniids and there has been much
discussion and redescription in the literature in an attempt to discern the epidemiology of
each species (Verster, 1969; Rausch, 1994; Hoberg et al., 2000; Thompson and McManus,
2002; Hoberg, 2006). Currently within the genus Taenia there are approximately 42
described species and 3 subspecies, while Echinococcus has a possible 9 species and
several strains of E. granulosus (Loos-Frank, 2000; Thompson and McManus, 2002;
Huttner et al., 2008; Huttner and Romig, 2009). However, it should be noted that many
‘strains’ of E. granulosus have recently been awarded species status (Thompson and
McManus, 2002; Huttner et al., 2008). While complete lifecycles are not known for all
species of taeniids it has been found that in general these parasites have relatively high
definitive host specificity and relatively low intermediate host specificity (Verster, 1969).
There are some exceptions to this, such as E. granulosus and T. hydatigena being found in
Intermediate hosts
Definitive host
Chapter 6 – Detecting Taenia species in…
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several different species of definitive hosts (Verster, 1965, 1969). Within African wildlife,
top level carnivores such as lion (Panthera leo), hyaena (Crocuta crocuta, Hyaena brauni,
and Hyaena hyaena), jackal (Canis mesomelas and C.adustus) and African painted dog
(Lycaon pictus) are commonly definitive hosts for taeniids (Dinnik and Sachs, 1969;
Verster, 1969; Jones and Khalil, 1984). The African lion has been found to be a definitive
host for T. regis and T. simbae, hyaena species are definitive hosts for T. dinniki, T.
hyaenae, T. crocutae and T. olngojinei and the silver-backed jackal is host to T. madoquae
(Pellegrini, 1950; Mettrick and Beverley-Burton, 1961; Dinnik and Sachs, 1972; Jones and
Khalil, 1984). The transmission cycles of these Taenia species invariably involves several
wild ungulates, particularly antelopes, as the intermediate host. For example, species of
antelope such as impala (Aepyceros melampus), gazelle (Gazella spp.), kudu (Tragelaphus
spp.) and wildebeest (Connochaetes spp.) have been found to harbour the metacestodes of
T. crocutae, T. hyaenae, T. hydatigena, T. madoquae, T. olngojinei and T. simbae (Table
6.1) (Nelson and Rausch, 1963; Dinnik and Sachs, 1969; Verster, 1969; Dinnik and Sachs,
1972; Jones and Khalil, 1984).
Reports of taeniid species within the African painted dog have been few with the majority
being made in the first half of the 20th century. These early observations included T.
lycaontis, T. brauni and E. lycaontis (Ortlepp, 1934; Mahon, 1954; Baer and Fain, 1955)
all of which were later revised and found to be synonymous with T. hyaenae, T. serialis
brauni and E. granulosus respectively (Verster, 1969). Less disputable are observations
Chapter 6 – Detecting Taenia species in…
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Table 6.1 Definitive and intermediate hosts of Taenia spp. infecting African carnivores.
Taenia species Distribution Definitive host Intermediate host Metacestode location
T. crocutae Africa Hyaena sp. Antelope: eg. impala, kudu and duiker
Cysticerci – skeletal muscle
T. dinniki Africa Hyaena sp. Unknown Unknown
T. hyaenae
(syn T. lycaontis)
Africa Hyaena sp.
African painted dog
Antelope: eg. impala and sable Cysticerci – muscles, heart, tongue, diaphragm
T. hydatigena Cosmopolitan Dog and other canids Ruminants Cysticerci – pelvic regions, liver, lungs
T. multiceps Cosmopolitan Dog and other canids Sheep and goat Coenurus – CNS, brain
T. serialis Cosmopolitan Dog and other canids Lagomorphs Coenurus – intermuscular tissue, heart
T. s. brauni Africa Dog and other canids
African painted dog
Rodents and primates Coenurus – intermuscular tissue heart
T. madoquae Africa Silver-backed jackal Antelope (Madoqua sp.) Cysticerci – skeletal muscle
T. ovis Cosmopolitan Dog and other canids Sheep and other ruminants Cysticerci – skeletal muscle, heart, diaphragm
T. olngojinei Africa Spotted hyaena Antelope eg. Grants gazelle Cysticerci – intrasacral muscle
T. regis Africa African lion Antelope Cysticerci – skeletal muscle, liver, lung
T. simbae Africa African lion Antelope Unknown
Chapter 6 – Detecting Taenia species in…
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of T. pisiformis and E. granulosus infections within the painted dog (Ortlepp, 1934, 1938;
Nelson and Rausch, 1963; Young, 1975). Besides these individual findings, one
parasitological prevalence study has been conducted on painted dog packs within Kruger
National Park which identified the prevalence of taeniid species to be 30% (van Heerden et
al., 1995).
There have been relatively few other prevalence studies of taeniids in African carnivores
but two studies on lions observed a prevalence of 58% and 15% (Muller-Graf, 1995; Bjork
et al., 2000) and one study on hyaena reported 12.9% (Engh et al., 2003). Due to data for
these studies being obtained from faecal samples and the subsequent lack of adult worms,
identification of species was not made.
The presence of taeniids within wildlife does not pose an immediate threat to the definitive
host as most adult tapeworms do not invade or feed off host tissue and are therefore
considered non-pathogenic (Bowman et al., 2003). However, there is a risk of zoonotic
disease as humans can act as intermediate hosts for many of these taeniid species. Of the
two genera, species of Echinococcus are considered more pathogenic as these parasites
form large hydatid cysts in the organs of the intermediate host, resulting in hydatid disease
in humans (Eckert et al., 2001). Among the species of Taenia, which utilize canids as the
definitive host, are members that are also potentially pathogenic to people. Examples
include T. multiceps, T. serialis and T. s. brauni which have been known to cause cerebral
coenurosis and ocular coenurosis in humans (Vanderwick et al., 1964; Templeton, 1968;
Williams and Templeton, 1971; Ibechukwu and Onwukeme, 1991). Humans most at risk to
possible zoonoses in wildlife are those in communities situated near or in national parks,
Chapter 6 – Detecting Taenia species in…
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where human/wildlife interactions are more common. Whilst cerebral and/or ocular
coenurosis is relatively rare, hydatid disease has been found to be highly endemic in sub-
Saharan Africa with studies on nomadic pastoralists reporting a prevalence of between 0.1
and 5.6% (Macpherson et al., 1989; Magambo et al., 2006).
The aim of this study was to firstly determine the prevalence of taeniid species within wild
and captive populations of the African painted dog, secondly to identify the species
involved, which may assist in understanding sylvatic predator/prey transmission cycles and
thirdly, to identify any species which may pose a public health risk. These aims were
achieved by obtaining data from three wild and three captive populations for comparative
analysis. Identification of species was achieved by staining proglottids and molecular
characterisations, while the known predator/prey relationships within each study
population were used to infer sylvatic lifecycles.
6.2 Materials and methods
6.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia
during three field trips conducted between 2007 and 2009. The population within Zambia
was sampled in each of the three years while the population in Namibia was sampled in
two of these years (2008 and 2009). Samples in Zimbabwe had been collected in 2006 and
stored for later analysis. The samples from captive animals were collected from two zoo
populations in Australia (Perth Zoo, Monarto Zoo) and a rehabilitation facility in South
Africa. See Chapter 2 for a full description of sample collection methods.
Chapter 6 – Detecting Taenia species in…
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6.2.2 Parasitological techniques
Refer to Chapter 2 for a detailed description of microscopy methods. All parasite ova and
cysts observed were recorded, although only data for taeniid spp. are reported here. All
samples were then analysed using PCR protocols specific for taeniid species as described
below.
6.2.3 Identification of proglottids
Taeniid proglottids were fixed in 10% formalin and stained using two different methods.
For Semichon’s aceto-carmine stain (Semichon, 1924), proglottids were placed into
ethanol for 24 hours, 1 drop of Semichon’s stain was added and after 24 hours samples
were dehydrated in a series of ethanol dilutions, starting with 70% ethanol and finishing
with 100% ethanol. These were then cleared in methyl salicytate for 20 minutes and
mounted onto microscope slides in Canida balsam. For Harris’s haematoxylin stain
(Harris, 1900), formalin fixed proglottids were placed in a dilution (water and 1.5 drops) of
Harris’s haematoxylin overnight, then washed in 70% ethanol before being destained in
acid alcohol (2% HCl in 70% ethanol) for several minutes until specimens were pale pink
in colour. Destaining was halted in basic alcohol (ammonium hydroxide in 10 ml 70%
ethanol) for up to 15 minutes or until samples turned blue. Samples were then washed in
70% ethanol, dehydrated, cleared and mounted on slides as for Semichon’s stain.
Identification of proglottids was made on the morphology of the female genitalia of each
proglottid as described by Verster (1969) (Figure 6.2).
Chapter 6 – Detecting Taenia species in…
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Figure 6.2 A depiction of the genital atrium of T. crocutae as an example of the
morphological features used in identification of proglottids. From Verster (1969).
Appendix 1 displays the proglottid key used for identifying samples obtained in this study.
6.2.4 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted. The
remaining solid matter was used for DNA extraction using the Maxwell® 16 Instrument
(Promega, Madison, USA) as per the manufacturer’s instruction. In an attempt to reduce
the impact of inhibitors in carnivore faecal matter, the final elution was diluted to a 5:1
ratio with nuclease free water.
6.2.5 Amplification of Taeniid isolates at the 12S rRNA locus
A multiplex PCR at the 12S rRNA locus was used for differentiation of Taenia spp.,
Echinoccocus granulosus and E. multilocularis as per Traschel et al. (2007). Briefly, 5
primers (Cest1, Cest2, Cest3, Cest4 and Cest5) were used for amplification yielding a 267
bp product for Taenia sp, 117 bp for E. granulosus and 395 bp for E. multilocularis. The
Vaginal loops Vaginal sphincter muscle
Vas deferens loops
Cirrus pouch
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PCR reaction was performed in 50 μl volumes consisting of 2µl of extracted DNA, 10
ρmol of each primer, 25 μl of mastermix (Qiagen multiplex kit, Qiagen, Hilden, Germany)
and 18 μl H2O. The 267 bp amplicons representing Taenia sp. were sequenced using the
internal sequencing primer Cest 5seq, as described by Traschel et al. (2007). The PCR
product was purified using a Wizard SV gel and PCR Clean-up system (Promega,
Madison, USA) following the manufacturer’s instructions. Sequence reactions were
performed using the Big Dye Terminator Version 3.1 cycle sequencing kit (Applied
Biosystems) according to the manufacturer’s instructions. Reactions were electrophoresed
on an ABI 3730 48 capillary machine.
6.2.6 Data analysis
Prevalences of infection were expressed as a percentage of positive samples found by
microscopy with 95% confidence intervals calculated assuming a binomial distribution,
using the software Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in
prevalence between populations and years were tested using the Fisher’s exact test or Chi-
square test.
Resultant nucleotide sequences were compared with published sequences on NCBI
GenBank using the basic alignment search tool (BLAST). Further sequence analysis
conducted using the sequence alignment program Sequencher 4.8™ (Gene Codes
Corporation, Ann Arbor, USA). The levels of sequence differences (D), based on pairwise
comparisons, were calculated using the formula D = 1- (M/L), where M is the number of
alignment positions at which the two sequences have a base in common and L is the total
Chapter 6 – Detecting Taenia species in…
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number of positions over which the sequences are compared (Chilton et al., 1997). The
level of sequence difference was expressed as a percentage.
Phylogenetic analysis was conducted in MEGA 4 (Tamura et al., 2007) using reference
sequences for T. multiceps, T. serialis, and E. granulosus (accession numbers GQ228819,
DQ408418, EU219546, DQ104238 and GQ161844 respectively). The neighbour-joining
method was used to infer phylogenetic relationships between sequenced isolates and
reference sequences, with support for nodes in the phylogeny assessed using a bootstrap
test with 1,500 replicates (Saitou and Nei, 1987).
6.3 Results
6.3.1 Prevalence of Infection
Table 6.2 shows the prevalence of infection with taeniid spp. within captive and wild
populations. Prevalence of infections with species of taeniid did not differ significantly
between the three wild populations (Fisher’s exact tests; Zambia vs. Namibia P=0.4;
Zambia vs. Zimbabwe P=1.00; Namibia vs. Zimbabwe P=0.7). There was a significant
difference between pooled data of wild and captive populations as taeniids were not
observed in any of the captive populations sampled (Fisher’s exact test, P < 0.0001).
Chapter 6 – Detecting Taenia species in…
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Table 6.2 Prevalence of taeniids (with 95% confidence intervals in parentheses) detected
in faecal samples from wild populations of the African painted dog.
Zimbabwe
(n=12)
Zambia
(n=43)
Namibia
(n=28)
Total wild
(n=83)
Total captive
(n=130)
33% 35% 25% 31.3% 0
(12 – 63%) (22 – 50%) (12 – 44%) (22 – 42%)
Data was obtained over three years for the Zambian population and two years for the
Namibian population. Taeniids were observed in each year with prevalences ranging from
14% to 89% (Table 6.3). There were significant differences in prevalences among years
within the Zambian population (χ2 = 15.03, P=0.001) but not in the Namibian population
(Fisher’s exact test, P=0.9).
Table 6.3 Prevalence of taeniids observed in the Zambian and Namibian populations of the
African painted dog over a three year period. Sample size (n) and 95% confidence intervals
in parentheses.
Population Year
2007 2008 2009
Zambia
89% (n=9)
(56 – 99%)
25% (n=20)
(10 – 47%)
14% (n=14)
(26 – 43%)
Namibia
26.3% (n=19)
(11 – 50%)
22% (n=9)
(41 – 56%)
-
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6.3.2 Identification of taeniid spp. proglottids
Five of the nine proglottids obtained from two packs within Zambia were tentatively
identified using the morphological features of the female genital atrium, including the
presence/absence of a vaginal sphincter muscle and the number of loops in the vas deferens
and vagina (Figure 6.2). Table 6.4 lists the morphological data for each of the five
proglottids. Using the criteria of Verster (1969) and Jones and Khalil (1984), one
proglottid resembled that of T. hydatigena, two resembled T. crocutae, one resembled T.
ovis and one resembled T. dinniki.
Table 6.4 Species identification of taeniid proglottids obtained from painted dog
populations.
Population Isolate Host sex
Host age
Morphological characters Probable species
Zambia ZKa01 M Yearling Vaginal sphincter = full Vaginal loops = 2 Vas deferens loop = 2/3 bunched towards end of cirrus pouch
T. dinniki
Zambia ZKa06 F Yearling Vaginal sphincter = full Vaginal loops =0 Vas deferens loops = 2
T. ovis
Zambia ZKa08 ? ? Vaginal sphincter = full Vaginal loops = 1 Vas deferens loops = 3
T. crocutae
Zambia ZRh18 M Adult Vaginal sphincter = 0 Vaginal loops = 1 Vas deferens loops = 2
T. hydatigena
Zambia ZRh26 ? ? Vaginal sphincter = full Vaginal loops = 1 Vas deferens loops = 3
T. crocutae
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6.3.3 Molecular characterisation of taeniid sp. isolates
The multiplex PCR used in this study was able to differentiate between Taenia spp., E.
granulosus and E. multilocularis at the 12S rRNA locus (Figure 6.3).
Figure 6.3 Multiplex PCR of taeniid isolates from wild painted dog populations at the 12S
rRNA locus. Lanes 2-11 are painted dog samples from Zambia and Namibia. Lane 13 is
the negative control; 14-16 are the positive controls for Taenia sp, E. granulosis and E.
multilocularis.
Of the 26 samples identified positive for taeniid ova by microscopy, 22 were successfully
amplified using the multiplex PCR. All of these were species of Taenia. Of the 22
amplicons, 16 were sequenced. Comparisons to published sequences on NCBI GenBank
revealed 3 sequences to be similar to T. hydatigena and 13 to have a similar identity to
both T.multiceps and T.serialis (Table 6.5).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Chapter 6 – Detecting Taenia species in…
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Table 6.5 Genotypic characterisation of taeniid spp. species isolates obtained from wild
populations of the African painted dog within Zambia, Namibia and Zimbabwe.
Percentages shown for matched identities with published sequences on GenBank in
parentheses.
Population Isolate No Host sex Host age Taenia species
Zambia Z-Ka01 M Yearling T. serialis (96) T. multiceps (96)
Zambia Z-Ka02 F Adult T. serialis (96) T. multiceps (96)
Zambia Z-Ka05 F Adult T.serialis (96) T. multiceps (96)
Zambia Z-Ka06 F Yearling T. serialis (96) T. multiceps (96)
Zambia Z-L01 F Adult T. serialis (96) T. multiceps (96)
Zambia Z-G01 F Adult T. serialis (89) T. multiceps (89)
Zambia Z-Rh01 M Adult T. hydatigena (99)
Zambia Z-Rh14 M Adult T. serialis (96) T. multiceps (96)
Zambia Z-Rh18 M Adult T. hydatigena (96)
Zambia Z-Rh29 F Adult T. hydatigena (89)
Namibia N-K17 ? Adult T. serialis (95) T. multiceps (97)
Namibia N-B08 ? ? T. serialis (95) T. multiceps (97)
Namibia N-T15 ? ? T. serialis (95) T. multiceps (97)
Zimbabwe Zw-Mo14 F pup T. serialis (95) T. multiceps (95)
Zimbabwe Zw-Mo12 ? ? T. serialis (89) T. multiceps (90)
Zimbabwe Zw-Ui01 M ? T. serialis (95) T. multiceps (96)
Chapter 6 – Detecting Taenia species in…
123
To clarify these BLAST results, nine sequences which had minimal ambiguities and
maximum bp regions were aligned against reference sequences for T. serialis and T.
multiceps, using the alignment program Sequencher 4.8 ™. Single nucleotide
polymorphisms (SNP’s) were identified between the two geographic regions and also
between the painted dog isolates and the reference sequences (Table 6.6).
Table 6.6 Summary of the nucleotide variations detected between taeniid isolates from
Zambian and Namibian populations of the African painted dog and reference sequences for
T. multiceps and T. serialis (GenBank accession numbers GQ228818, DQ408418 and
EU219546, DQ104238). Alignment was conducted in Sequencher™ 4.8 and dots indicate
identity with the first sequence.
Taenia isolates Alignment position
487 492 493 496 524 577 594 612
T. multiceps A A T G G C G T
T. serialis . . . . . T . .
Z-Rh14 – Zambia T G T A A T . C
Z-Ka06 – Zambia T G T A A T . C
Z-Ka02 – Zambia T G T A A T . C
Z-L01 – Zambia T G T A A T . C
Z-Ka01 – Zambia T G T A A T . C
Z-Ka05 – Zambia T G T A A T . C
N-B08 – Namibia T G C A A C A T
N-K17 – Namibia T G C A A C A T
N-T15 – Namibia T G C A A C A T
Chapter 6 – Detecting Taenia species in…
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Intraspecific variation was calculated using pairwise comparisons (Table 6.7). Low
intraspecific variation was detected within T.multiceps and T.serialis reference
sequences (0 – 0.6%) and within Zambian and Namibian isolates (0.5 – 0.9%).
Pairwise comparisons between the painted dog isolates from both populations and the
reference sequences were somewhat higher (3.0 – 4.9%).
Table 6.7 Pairwise comparison of sequence variation (%) within the 12S rRNA loci of
T. multiceps and T. serialis reference sequences and taeniid isolates obtained from
Namibian and Zambian populations of the African painted dog.
T.multiceps T.serialis Zambian
isolates
Namibian
isolates
T. multiceps (n=2) 0 4.1 3 – 3.5 2.9 – 3.9
T. serialis (n=2) - 0.6 3 – 3.5 3.9 - 4.9
Zambian isolates (n=6) - - 0 – 0.5 2.5 - 4
Namibian isolates (n=3) - - - 0 – 0.9
T. multiceps (accession numbers GQ228819, DQ408418), T. serialis (accession
numbers EU219546, DQ104238), Zambian isolates (Z-Ka01, Z-Ka02, Z-Ka05, Z-
Ka06, Z-L01, Z-Rh14), Namibian isolates (N-T15, N-K17, N-B08).
6.3.4 Phylogenetic analysis of Taenia spp. isolates
Figure 6.4 represents the phylogenetic relationship between the sequenced isolates from
this study and reference sequences obtained from GenBank for several species of
Taenia. Geographic grouping can be observed within the painted dog isolates. Isolates
Chapter 6 – Detecting Taenia species in…
125
from the painted dogs are not completely aligned with T. multiceps or T. serialis
suggesting significant variation exists between them.
Figure 6.4 Phylogenetic relationships, inferred using the Neighbour-joining method
between taeniid isolates from African painted dogs and reference isolates of T.
multiceps and T. serialis based on sequence data of the 12S rRNA locus.
Representatives of Taenia sp. used for comparison are labelled with accession numbers
as published on GenBank, with E. granulosus as the out-group. Numbers at nodes refer
to bootstrap values (1,500 replicates) > 20%.
6.4 Discussion
Taeniid species were not detected within any of the captive populations of the African
painted dog. This was most likely a reflection of the captive environment which
involves a modified diet of pre-frozen domestic livestock meat and regular anthelmintic
Chapter 6 – Detecting Taenia species in…
126
treatment inhibiting parasite transmission (see Chapter 2). In comparison, the total
prevalence of taeniid spp. observed in the wild study populations was 31.3%. This was
similar to the prevalence reported by van Heerden et al. (1995) in painted dogs (30%).
Studies on competitor species have reported prevalences of 13% in hyaena and 15%
and 58% in lions (Muller-Graf, 1995; Bjork et al., 2000; Engh et al., 2003).
Prevalence of infection in this study was not significantly different between geographic
regions, although a significant difference was observed between years in the Zambian
population. This was mainly due to the high prevalence observed in the first year of
sampling (2007), which also had the majority of samples collected in the wet season.
Taeniid ova are resilient, but prolonged high temperatures can reduce survivability and
subsequently transmission rates are decreased (Lawson and Gemmell, 1983). The
higher prevalence observed in the wet season may also be a reflection of increased
predation, leading to heightened transmission rates and subsequent improved host
condition, allowing for an increase in proglottid output (Mettrick and Munro, 1965).
Conclusive identification of Taenia species was not possible for all samples but with
the use of molecular characterisation, morphological data and knowledge of possible
intermediate hosts, some tentative identifications can be made. The molecular
techniques utilized were successful in determining that the taeniid ova identified
through microscopy were not the pathogenic zoonotic genera of Echinococcus but were
all Taenia species. Three isolates identified closely with T. hydatigena, which
correlated with the identification of a proglottid obtained from one of these samples.
Identification of the remaining 13 isolates was undetermined as a BLAST on GenBank
revealed isolates had similar a identity to both T. serialis and T. multiceps. Pairwise
comparisons of intraspecific variation within the reference sequences were low at 0.6%
Chapter 6 – Detecting Taenia species in…
127
for T. serialis and 0% for T. multiceps. In comparison, a much higher variation was
observed between T. multiceps and T. serialis and the Zambian isolates (3.4% and
3.5%) and the Namibian isolates (2.9% and 4.9%). This suggests that the painted dog
isolates are genetically distinct from the reference sequences. Additionally, the
variation between sequences from each geographic region was equally high (2.5% -
4%). This was also implied in the phylogenetic tree, where the isolates from Zambia
and Namibia grouped separately and apart from T. multiceps and T. serialis. These
results indicate that the taeniid species found in African painted dogs in this study are
not T. multiceps or T. serialis and are most likely an as yet unsequenced African Taenia
species. It would also appear that there are different species infecting the different
geographic regions. The inability to conclusively identify these isolates is most likely
due to the lack of genetic information available for the rarer African Taenia species
such as T. crocutae, T. hyaenae and T. dinniki.
The probability that the infecting species were of African origin was supported with the
identification of proglottids. Whilst the use of only proglottids for the purpose of
species identification is not conclusive the morphology of reproductive organs can be
characteristic enough to discount some species (Verster, 1969). For example, the
presence of a full vaginal sphincter was able to discount T. multiceps as a possible
species as a ½ sphincter (pad) is specific to this species. As all proglottids had either a
full vaginal sphincter or a complete absence of one, this decreased the likelihood that T.
multiceps was the predominant species present as suggested by the molecular data.
Similarly, T. serialis was discounted due to the absence of an extended cirrus pouch
and variation between vaginal sphincters and number of loops in the vagina and vas
deferens. Additionally, a proglottid identified as T. dinniki had come from a faecal
sample from which the sequenced isolate matched with T. multiceps/T. serialis.
Chapter 6 – Detecting Taenia species in…
128
Without adult worms and/or the addition of molecular data of the rarer African species
of Taenia to public databases, the identification of the predominant Taenia species
infecting these populations remains inconclusive. To date the only species of Taenia
reported in the painted dog have been T. pisiformis, T. s. brauni and T. hyaena
(Ortlepp, 1938; Mahon, 1954; Baer and Fain, 1955). While T. crocutae and T. dinniki
are both species previously found in hyaena, they may be shared with painted dogs as is
T. lycaontis (syn. T. hyaenae). The intermediate hosts for T. dinniki are presently
unknown, however, for T. crocutae they include antelope such as impala, lechwe, kudu
and duiker. These intermediate hosts are major food sources for the painted dog with
impala the dominant prey item within the Zambian population and kudu and duiker the
dominant prey item within Namibia (Lines, 2009).
Whilst Echinococcus species were not identified in this study E. granulosus has been
previously reported in the painted dog (Ortlepp, 1934; Nelson and Rausch, 1963;
Verster, 1965; Young, 1975). In particular, experimental infections found painted dogs
to be very susceptible to infection with Echinococcus protoscolices (Verster, 1961).
However, while the painted dog appears to be a suitable host, only a few observations
have been made. This low incidence may be due to the inability to differentiate taeniid
ova or perhaps more likely due to the lack of suitable intermediate hosts acting as prey.
Two studies in Kenya which conducted numerous necropsies on wild herbivores found
very few hydatid cysts within these animals (Nelson and Rausch, 1963; MacPherson et
al., 1983). These same studies presented evidence that the parasite was being
maintained between dogs and domestic livestock rather than sylvatic transmission. A
recent review on known intermediate hosts for hydatid cysts also noted that antelope
appear to play a minor role with very few observations from large sample sizes
Chapter 6 – Detecting Taenia species in…
129
(Huttner et al., 2009). Antelope are a major food source for the painted dogs in this
study and this may provide a reason for the absences of Echinococcus spp.
6.4.1 Conclusions
The prevalence of Taenia species observed in this study indicates that the painted dog
is an important definitive host for taeniid in all geographic regions sampled. Molecular
tools demonstrated that Echinococcus species were not cycling in any of the sampled
wild populations and therefore painted dogs should not be implicated in the spread of
hydatid disease in these regions. The most prevalent cestodes within all sampled
populations are perhaps one or more genetically uncharacterised Taenia species.
Molecularly these appear to be closely related to T. multiceps, a potential zoonotic
threat, but morphological data suggests other species such as T. crocutae and T. dinniki
are possible, both of which have unknown zoonotic potential. Additionally, there
appears to be geographic variation between the Zambian and Namibian isolates. This
was the first observation of Taenia hydatigena within the African painted dog and
possibly the first observations of T. multiceps and T. dinniki.
Molecular tools are allowing substantial advancements in the efforts to unravel the
phylogeny of Taeniidae but further work needs to be done on the lesser known Taenia
species of African carnivores. Increased surveillance and sample collection from wild
populations, combined with molecular characterisations will assist in understanding the
epidemiology of Taenia infection within this endangered carnivore.
Chapter 7 – General discussion
130
Chapter 7
General discussion
Chapter 7 – General discussion
131
7.1 Conservation status of the African painted dog
As habitat destruction and human encroachment continue, there is an ever increasing
need for conservation of wild species. The African painted dog has suffered a 99%
decline in population size in the last century, with approximately 3,000 animals left in
the wild environment today (IUCN, 2010). As an endangered species, African painted
dogs are more vulnerable to stochastic events such as disease outbreaks which can lead
to extirpations. It is therefore imperative to understand all threatening processes to
which these animals may be exposed. Parasitism is considered one such threatening
process for which a thorough understanding is still lacking.
The main aim of this study was to obtain detailed baseline data of parasitism within
populations of the African painted dog in both captive and wild environments. With
this information it was hoped to assist in the conservation of the painted dog by a)
recognising the challenges of parasite control in captive populations, particularly those
involved in reintroduction and/or translocation programs, and b) being able to identify
deviations from ‘baseline’ parasite levels in wild populations which could be
indications for emerging exotic and/or zoonotic diseases.
7.2 Increasing importance of studies of parasites
Parasite/host interactions within the natural environment generally involve
polyparasitism with variable host and environmental factors leading to complex and
dynamic systems. Parasitism within individual hosts and host populations can have
both negative and positive effects. Direct impacts cause disease whilst also develop
host immune systems, and indirect impacts mediate competitive and predatory
Chapter 7 – General discussion
132
interactions, whilst also drive genetic diversity. To add to these complex interactions,
the effects of outside stressors such as habitat destruction and human encroachment are
important influences which can easily disrupt the natural balance of many host/parasite
relationships. To attempt to understand the effects on any particular host species,
comprehensive data must first be obtained on the parasites that are present in natural
host populations, their prevalence and their relationship to host and environmental
variables. This study was successful in obtaining parasitological data on several wild
and captive populations over a three year period and currently represents the largest
parasitological study yet undertaken of the African painted dog.
7.3 Parasitological techniques
The use of traditional microscopy techniques in conjunction with molecular tools to
genetically characterise parasite species was found to be a successful combination for
this project. Microscopy techniques allowed for the identification of the majority of
parasites existing within a specific host along with an estimate of the intensity of
infection for each animal. However, many parasites could not be identified to species
level based on ova/cyst morphology and molecular characterisation was required in
order to obtain this information. Other studies using these techniques include those
which have successfully identified species of hookworm and Giardia in faecal samples
obtained from dogs and coyotes (Traub et al., 2004a; Palmer et al., 2008; Traub et al.,
2008; Thompson et al., 2009). Prior to use of this technology, the most common way to
identify parasite species was by obtaining adult specimens during necropsy of the host,
which still required considerable expertise in order to correctly identify specimens.
Euthanasia and subsequent necropsy is not an option when dealing with endangered
wildlife and finding animals which have died of natural causes in the field is extremely
Chapter 7 – General discussion
133
rare due to the efficiency of scavengers. Molecular techniques are therefore vital to
conduct complete parasitological diagnostics within endangered, wild populations. The
combination of microscopy and molecular methods have allowed this project to provide
significant information on parasite infracommunity composition, intensity of infection
within populations and also the pathogenic and zoonotic risks posed by species such as
Giardia duodenalis, Taenia spp. and Ancylostoma spp.
7.4 Implications for biodiversity conservation
As discussed in Chapter 1, parasites make up a large part of the biodiversity in natural
ecosystems and have co-evolved to form complex relationships with their host and
surrounding environment (May and Anderson, 1983; Poulin and Morand, 2000).
Therefore, parasites warrant consideration for conservation programs in their own right.
Of particular concern would be species of parasites that are host specific and run the
risk of becoming extinct with the host. With reference to this study some parasite
species could not be completely identified, leaving the possibility that host specific
parasites exist within painted dog populations. For example, the majority of sequenced
isolates of Taenia spp. obtained from wild populations were not completely matched
with the available genetic information. It is possible that the species of Taenia infecting
these animals are known species which are not yet genetically characterized or they
could be previously unidentified species unique to the painted dog. As the painted dog
is an endangered carnivore, the risks of co-extinction events occurring with this host
are significant. It is possible that there is the risk of losing species before science has
even been introduced to them.
Chapter 7 – General discussion
134
7.5 Parasitism in natural populations
7.5.1 Baseline data
This study has gained an insight into the natural abundance, prevalence and intensity of
parasitism within wild populations of the painted dogs over several geographic regions.
The similar parasite community compositions observed among all three wild
populations during the three year study suggest that this represents the ‘natural’ parasite
fauna of the African painted dog. These data can therefore be confidently used as a
baseline for the GI parasites infecting wild populations of the African painted dog, and
can be used for comparisons with future results. Few studies have been able to obtain
this information with most conducting single random sampling studies which are
unable to provide comprehensive data on the host/parasite systems. The need for this
data has been noted by several authors of similar studies who have only been able to
conduct single studies on small population, such as those conducted on the African lion
and spotted hyaena (Bjork et al., 2000; Engh et al., 2003)
Of the seven GI parasite genera observed in populations of the African painted dog,
five have not been previously reported. Within the two genera previously reported
(Taenia and Ancylostoma), three species are reported here for the first time
(Ancylostoma braziliense, Taenia hydatigena and T. dinniki). This large proportion of
new discoveries demonstrates the paucity of information currently available on
parasitism within this host species and is a reflection of the limited knowledge of
parasitism in wildlife in general.
Chapter 7 – General discussion
135
7.5.2 Parasite threats to painted dogs
The ecology of the African painted dog plays a pivotal role in its exposure to parasitic
disease and potential disease outbreak within populations. Social aspects of the pack
such as the maintenance of close contact by all animals can lead to the rapid spread of
directly transmitted parasites such as hookworm and Giardia spp. Likewise, feeding on
the same prey items results in the same exposure to indirectly transmitted parasites such
as Sarcocystis spp. and Taenia spp. Painted dog packs are renowned for having large
roaming areas (<2,000 km2) which raises the likelihood of packs moving through
human communities and contracting disease from domestic animals, particularly
domestic dogs. The exposure of one member of the pack to disease will then be likely
to result in all members becoming infected. Finally, as populations of painted dogs
appear to exist at natural low densities they are particularly vulnerable to catastrophic
events such as disease which can result in local extinction.
It was difficult to ascertain clinical effects of parasitism within wild populations as
visually all animals appeared to be strong and robust. The only obvious clinical signs
were from those animals carrying injuries i.e. broken legs or snare line injuries. This
appearance of apparent health is common within the natural environment as most wild
animals tend to manifest few recognizable signs of disease (Sachs and Sachs, 1968;
Young, 1969; Roberts et al., 2002). The effects of parasitism on the African painted
dog are therefore most likely to be at a subclinical level. With reference to the findings
in this project, parasites such as Giardia duodenalis could result in sub-clinical disease,
particularly on populations with a low nutritional status or during periods of stress.
Likewise, the intensity of hookworm infection may cause clinical disease in
immunocompromised animals, such as old, injured or stressed individuals. Evidence
for this has been seen in the death of an immunocompromised captive painted dog due
Chapter 7 – General discussion
136
to a hookworm infection, and stress has been suggested as a cause for clinical
babesiosis observed in wild rhinoceros and lion (van Heerden, 1986; Penzhorn, 2006).
7.5.3 Zoonoses/anthropozoonoses
Wildlife are often implicated as reservoirs for zoonotic disease and are therefore
considered a threat to surrounding human communities and livestock. The results from
this study suggest the painted dog is not a major threat for zoonotic disease. Of the
parasites observed, the taeniids, Giardia duodenalis and hookworm are potential
zoonotic threats. Within the taeniids, the genus Echinococcus is considered the more
pathogenic as it can cause hydatid disease in humans. Although there was no evidence
of this genus in any of the wild populations of painted dogs which were sampled, the
unidentified Taenia spp. cannot be discounted as potential zoonoses.
The observation of the zoonotic assemblages of G. duodenalis in wild populations
raised the question of whether painted dogs may transmit this parasite to people, but
given the lack of direct contact between these animals and humans, transmission from
painted dogs is unlikely. However, increased human activity into areas such as national
parks has the potential to increase the prevalence of G. duodenalis infection in the
painted dog. Human to animal transmission (anthropozoonotic) is not well understood
or recognised but there has been some evidence for this occurring. Examples include
the transmission of Giardia spp. from human faecal contamination into populations of
gorillas in Uganda and beavers in North America (Bemrick and Erlandsen, 1988;
Graczyk et al., 2002; Fayer et al., 2006). Similarly, the observation of Ancylostoma
braziliense in this study indicates a zoonotic risk but again the lack of direct human
contact would indicate the risk of transmission from painted dogs in the wild
environment would be minimal.
Chapter 7 – General discussion
137
7.6 Parasitism in captive populations
This is one of few studies to directly compare levels of parasitism between captive and
wild environments in a specific host. A significant difference was observed between the
two environments with 15% of captive and 99% of wild animals found to be host to
one or more parasite species. The implications of the lower exposure to parasites
observed in captive populations may be significant, particularly for those involved in
reintroduction programs, as immunologically naïve animals will be more susceptible to
clinical disease (Viggers et al., 1993; Kock et al., 2010).
The management of captive animals is governed by the need for healthy and
reproductively sound animals and therefore parasite control is a major consideration.
Often the objective is to completely eradicate all parasites from the resident populations
but this may also result in extinction of host-specific parasites (Gompper and Williams,
1998). Additionally, as captive breeding facilities move toward conducting
reintroduction programs, management of captive animals may need to alter the focus
from complete parasite eradication to allowing a low level of parasitism to exist within
the population. In the short term this may assist in the development and maintenance of
host immunity which will be required when animals are reintroduced back into the wild
environment. The most pertinent example of this that is relevant to this study is the
observed prevalence of hookworm in the wild environment (32.5%) compared to the
complete absence in the captive environment. Exposure to a large burden of hookworm
by immunologically naïve painted dogs would most likely result in severe anaemia and
possible death as seen in domestic dogs (Miller, 1971; Carroll and Grove, 1985).
However, if captive animals had prior exposure to this parasite and had developed low
levels of immunity this effect would be minimized (Carroll and Grove, 1985). In the
long term, parasite exposure has been shown to assist in maintaining genetic diversity,
Chapter 7 – General discussion
138
particularly of the major histocompatibility complex (MHC) which is largely involved
in immune function (Paterson et al., 1998). As a major concern of captive breeding is
loss of genetic diversity this beneficial effect of parasitism may outweigh the
occasional loss of an animal due to the direct effects of parasitism.
7.7 Project limitations and future research
7.7.1 Sample collection and analysis
The logistics of field work prevented sufficient sampling of all wild populations in
order to answer all hypotheses. For example, the lack of samples from pups did not
allow for the significance of host age to be sufficiently tested. In addition, sampling
was predominantly restricted to faecal samples and it was therefore not possible to
detect parasites such as Toxoplasma spp., Sarcocystis spp., Babesia spp, and
Dirofilaria immitis (heartworm) existing in host blood or tissues.
The use of fresh samples is preferred for accurate detection of parasite stages but the
lack of facilities in the field meant that samples had to be preserved in 10% formalin
and 70% ethanol for shipping and later analysis. Several microscopy techniques were
employed in an effort to observe all parasite species, however, the most accurate
method for prevalence data is usually obtained during necropsy. This method was not
an option for studies on endangered wildlife and finding carcasses in the field did not
occur during the course of the project.
The molecular techniques employed were of great value in identifying several parasite
species, however not all positive samples could be amplified by PCR. In the case of
Chapter 7 – General discussion
139
hookworm only a small subset of samples was successfully amplified and sequenced.
Additional sequences would have been beneficial in providing detailed information on
the prevalence of species infecting packs and also in obtaining accurate geographic
distributions for the hookworm species observed. Finally, as the use of molecular
techniques is relatively new not all species of parasites have been genetically
characterised and sequences are therefore not available for comparison in databases.
This was the case with the predominant Taenia spp. observed in this study which
remains unknown despite the successful amplification and sequencing of many
samples.
7.7.2 Continued surveillance
The data obtained from this study has provided a baseline for the ‘normal’ parasite
diversity and prevalence of GI parasites to which painted dogs are exposed within the
natural environment. This information can now be used to identify future deviations
from this baseline which may then assist to identify potential emerging disease. In
order for this to be of use, continued surveillance of parasitism within painted dog
populations needs to be conducted. The data from this study, used in conjunction with
results from future surveillance, may also help to predict how continued pressure on the
already small populations existing in the wild may change the dynamics of the
host/parasite systems currently in play. The host/parasite relationship is often a careful
balance which can be tipped in favour of the parasite if the host is immunologically
compromised. For instance, the decreased hunting success in small painted dog packs
may lead to a lowered nutrition plane which could in turn lead to immunocompromised
animals. Other factors such as habitat destruction, human encroachment and disease
may also result in an imbalance in the host/parasite relationship leading to an increase
in clinical disease.
Chapter 7 – General discussion
140
7.7.3 Threat of emerging disease
As outlined throughout this thesis the host/parasite interaction is complex and dynamic.
These interactions will be further complicated by human influences such as habitat
destruction and human encroachment. Habitat destruction disturbs ecosystems and can
subsequently alter host/parasite interactions. Evidence for this was seen in a study by
Gillespie et al. (2005) which identified altered patterns of parasite infection among red
tailed guenon populations living in unlogged and logged habitats. Likewise, human
encroachment brings the increased risk of disease spillover from co-habiting domestic
animals. As approximately 80% of domestic animal pathogens can infect wildlife the
threat is significant (Cleaveland et al., 2001). The painted dog has already been seen to
be vulnerable to domestic dog diseases such as rabies and canine distemper virus
suggesting they could be vulnerable to additional disease spillover (Kat et al., 1995;
Roelke-Parker et al., 1996). The identification in this study of predominantly zoonotic
assemblages of Giardia duodenalis in the painted dog may be indicative of human
encroachment and consequently should be considered an emerging disease within this
species. Future parasitological studies comparing results to this newly obtained baseline
may be able to predict and identify future emerging diseases.
7.7.4 Captive management
This project was only able to conduct a captive versus wild comparison for a single
host species but given the significance of results obtained, could be used as a model for
other host species. As reintroduction programs become a main aim for many captive
facilities a host specific knowledge of parasitism in the natural environment may
provide important information. The ability to predict the type of parasitic challenge that
reintroduced hosts may face could lead to vaccination programs or deliberate exposure
to specific parasites in order to increase the chance of successful reintroduction.
Chapter 7 – General discussion
141
Additionally, these parasitological studies may prevent future introductions of exotic
pathogens from reintroduced captive stock into naïve wild populations (Viggers et al.,
1993; Kock et al., 2010). Similar studies on other endangered captive host species
could, therefore, be of benefit to many reintroduction and/or translocation programs.
142
Appendix 1. Taenia spp. proglottid key. From Verster (1969)
143
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