introduction to protozoan parasites

....much of which is parasiticThe majority of eukaryotic life is protozoan...

Protozoa

alveolates

Fecal-oral

Foodborne

Mode of transmission

Coccidians

Cryptosporidium

Excavates

LeishmaniaTrypanosoma

ApicomplexaCiliates DinoflagellatesHeterolobosia Euglenoza Fornicata

major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector

ToxoplasmaPlasmodium

'brain-eatingamoeba'

'traveler's diarrhea'


malariaChagas diseaseAfrican sleeping sickness

Kala azar

Phylogeny of protozoan parasites

kinetoplastids

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

Kinetoplast - defining feature of all kinetoplastids

kinetoplastids

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar


kinetoplastids

Lukes, Euk. Cell, 2002

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

kinetoplastids

Lukes, Euk. Cell, 2002

Hajduk, FASEB, 1993


Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

defining features of alveolates

The Inner Membrane Complex (IMC) underlies the parasite plasma membrane

6IMC: flattened vesicles + cytoskeletonToxoplasma

ER

Mt

DG

PM

IMCPM

IMCThe Inner Membrane Complex (IMC) underlies the parasite plasma membrane

6IMC: flattened vesicles + cytoskeletonToxoplasma

ER

Mt

DG

PM

IMCPM


6IMC: flattened vesicles + cytoskeleton

Gliding machinery: - MyoA - MLC1 - GAP45 - GAP50 - GAP40

Toxoplasma

ER

Mt

DG

PM

IMCPM


6IMC: flattened vesicles + cytoskeleton

Cytoskeletal elements: - Microtubules - Alveolins - GAPMs - ISPs

Gliding machinery: - MyoA - MLC1 - GAP45 - GAP50 - GAP40

Toxoplasma

Spatial-temporal organization of the IMC is critical for Plasmodium differentiation

7

MD Lazarus et al, J Cell Sci 121:1937-‐49; 2008 LG Tilney, unpublishedMD Lazarus et al, J Cell Sci 121:1937-‐49; 2008

Parasitophorous vacuole (PV) Parasite Plasma Membrane Inner Membrane Complex (IMC)

Merozoite Trophozoite Schizont

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

defining features of apicomplexa

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

defining features of apicomplexa

> 5000 species of parasites

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar


kinetoplastids

Interpreting parasite life-cycles


• What is the definitive host (sexual reproduction)?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?• Can there be more than one host species?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?• Can there be more than one host species?• How are the host species geographically distributed?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?• Can there be more than one host species?• How are the host species geographically distributed?• How does transmission occur?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?• Can there be more than one host species?• How are the host species geographically distributed?• How does transmission occur?• What cell type(s) does the parasite infect?


• What is the definitive host (sexual reproduction)?• What is the intermediate host (asexual reproduction)?• Can there be more than one host species?• How are the host species geographically distributed?• How does transmission occur?• What cell type(s) does the parasite infect?• What are the major developmental stages?

gut gut

Red blood

cells

Sporozoites

into host

Sexual stages

in vector

Intestinal epithelium

Salivary glands

Intestinal

epithelium

Merozoites

Toxoplasma

Crypto- sporidium

Plasmodium

Theileria

Tick

M

osqu

ito

Cat

(Muscle,

neurons)

Mammalia

n

Host

Hep

atoc

ytes

Lym

phoc

ytes

Any

cel

l

(Bradyzoites)

Roos, Science 309:72-74 (2005)

Apicomplexa share similar life-cycle strategies

Toxoplasma life-cycle

Hunter & Sibley. Nature Rev. Micro. 2012



Intermediate host!(asexual reproduction)



initial infection leads rapid cell invasion and parasite replication

from Gary Ward!Univ. of Vermont

Intermediate host!(asexual reproduction)

Dinkorma Ouologuem

14



Asexual reproduction occurs in intermediate hosts

Toxoplasma life-cycleSexual reproduction occurs in Felidae (definitive host)

18Kreuder, et al., J. Wildlife Diseases, 2003

18Conrad, et al., IJP, 2005Kreuder, et al., J. Wildlife Diseases, 2003

18Conrad, et al., IJP, 2005Kreuder, et al., J. Wildlife Diseases, 2003

Torey & Yolken, TrePar, 2013

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar


kinetoplastids

Cryptosporidium: sexual and asexual reproduction occur in the same tissue of the same host

very resilient!common contaminant of water

ID50 = 100-300 cysts

Cryptosporidium = ‘hidden spore’

NEJM, March 1995


NEJM, March 1995


~400,000 people affected!69 people died (93% had HIV/AIDS)

• GEMS set out to identify infectious causes of mild to severe cases of pediatric diarrhea in developing countries !• 7 study sites in Africa and SE Asia; 3 year study!• ~10,000 children with MSD and ~13,000 controls (0-5yrs)!• multiplex diagnostics leveraging a variety of molecular and standard microbiological assays.

The Lancet, July 2013

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar


kinetoplastids

Plasmodium life-cycle

Malaria

MalariaRanks as one of the ‘big three’ in

total mortality for infectious diseases



220 million people infected in 2010




most are in sub-Saharan Africa





over 600,000 deaths in 2010 alone






90% of these are in children under age 5






90% of these are in children under age 5

global prevalence has dropped 25% since 2000

Why is malaria so deadly?

Miller, et al., Science, 1994 vol. 264: 1878-1883.

Why is malaria so deadly?

P. vivax

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar


kinetoplastids

Leishmaniasis

cutaneous

Leishmaniasis

cutaneous mucocutaneous

Leishmaniasis

cutaneous mucocutaneous visceral

Leishmaniasis

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

kinetoplastids

African Trypanosomes"T. bruci rhodesiense (East African Sleeping Sickness) - only 2% of disease, acutely progressive!T. bruci gambiense (West African Sleeping Sickness) - accounts for 98% of disease

tsetse fly

humans!buffaloes!

cattle

T. brucei (African sleeping sickness)

Only 1% of tsetse flies are infected

Protozoa

alveolates

Fecal-oral

Foodborne


Coccidians

Cryptosporidium

Excavates



major subgroup

Phylum

Genus

Naegleria Giardia

Insect vector






Kala azar

kinetoplastids

American Trypanosomiasis"T. cruzi (Chagas disease)

T. cruzi is transmitted by reduviid bugs

T. cruzi life-cycle

introduction to protozoan parasites

Science

parasite plasma membrane

inner membrane complex

pm imcpm imc

attened vesicles

cytoskeleton toxoplasma

gap40 toxoplasma

cytoskeleton gliding

myoa mlc1