english: dr. vett lloyd
TRANSCRIPT
Comparing results and predic2ons of different surveillance approaches for Lyme borreliosis Canine seroprevalence in New Brunswick as a case study
Dr. Vett Lloyd
Mt. Allison University
Faculty/Presenter Disclosure • Faculty: Ve3 Lloyd
• Rela2onships with commercial interests: – Grants/Research Support: NSERC – Speakers Bureau/Honoraria: Academic only – Consul2ng Fees: None – Other: Employee of Mt. Allison University
Disclosure of Commercial Support • This program has received financial support from NSERC in the form of
Discovery Grant, MITACS grant.
• Poten2al for conflict(s) of interest: • None
MiHgaHng PotenHal Bias
• NSERC does not dictate or prescribe research results.
Content: 1. Different surveillance approaches and the role of canine seroprevalence studies
2. Canine seroprevalence in New Brunswick
. Surveillance of Hcks in New Brunswick, 2012-‐1015. Julie Lewis, Ve3 Lloyd. Unpublished.
Lyme disease risk in Dogs in New Brunswick Natalie K. Bjurman1, Gina Bradet2, Ve3 K. Lloyd1,3 CVJ, in press
Surveillance for 2cks and 2ck-‐vectored diseases
November 3rd 2014
AcHve Hck surveillance
Canine seroprevalence
Passive Hck surveillance
Human case reports
Labour intensive and expensive Low sensiHvity
Under-‐reporHng
Used extensively in US, Europe and Asia Limited use in Canada PaHcularly useful in areas of emerging risk
h3p://www.express.co.uk/news/nature/439432/Mystery-‐of-‐killer-‐canine-‐disease-‐spreading-‐from-‐the-‐New-‐Forest
Why this works:
h3p://www.dog-‐care-‐knowledge.com/dog-‐Hck-‐removal.html
h3p://www.wellcomeimageawards.org/2014/Hck-‐sucking-‐blood-‐from-‐human-‐leg
Humans and dogs get Lyme disease in the same way
Advantages –informaHon on canine Lyme is rouHnely collected by veterinary clinics using standardized and validated methodologies. It is freely available on line which is valuable for public awareness and educaHon.
Pet Disease Report -‐ IDEXX h3p://www.petdiseasereport.com/content/prevmap.aspx?currentprev=LS
New Brunswick as a case study on the use of canine seroprevalence as a predictor of human Lyme disease risk
Why New Brunswick?
Leiske, D and V. Lloyd – in review
Surveillance of Hcks in New Brunswick, 2012-‐1015. Julie Lewis, Ve3 Lloyd. Unpublished.
Why • Live with humans • Robust immune response
• When ill, similar clinical manifestaHons of disease (symptoms) ie arthriHs, lameness, and neurological disease
• InfecHon detected with commercial kits
Methods
nutrasilver.com
How • Recruitment of veterinary clinics • 100 canine blood samples for each of
the 7 NB health districts • Tested 699 samples using IDEXX
Snap4Dx+C6 ELISA and immunoblot • Risk factor correlaHon
Borrelia infec2on (Lyme disease risk) in Dogs in New Brunswick Natalie K. Bjurman1, Gina Bradet2, Ve3 K. Lloyd1,3
Results
Rapid recent increase in canine seroposi2vity (6 fold in 6 years) Western blohng results were generally consistent with C6 ELISAs but both tests had false posiHves and possibly false negaHves There is no accepted algorithm for interpretaHon of western blots and posiHve/negaHve calls varied by algorithm
So what does this mean for humans?
1:6 raHo of human:dog infecHons
6,475 humans with Lyme
New Brunswick Public Health
5
Re-‐assessment approach
ProporHon of infected Hcks (I)
Number of infected humans
X X = x
x
x
x x x x x
ProporHon engorging on humans(F)
Number of Hck bites (T)
X X = x
x
x
x x x x x
ProporHon of infected Hcks (I)
ProporHon engorging on dogs (F)
Number of Hck bites (T) Number of infected dogs
Propor2on of infected 2cks -‐ I
I = 0.123 (NML low value .068, high value .159)
Ogden et al. 2006 Dibernardo et al 2014 Lewis and Lloyd (in prep) 1990-‐2003 2012 2014 151 364 536 15.9% 6.8% 12.3%
year
Number tested
% infecHon
Propor2on of fed 2cks -‐ F
F = 0.614 /0.08 (humans) or 0.974/.60 (dogs)
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10
BL/SL ra2o
BW/SW ra2o
NB 2014 Hcks
Literature
Tick size vs 2me feeding
72hrs
0-‐24h 19 1-‐2 days 1 2-‐3 days 3 3+ days 2
0-‐24h 25 1-‐2 days 18 2-‐3 days 97 3+ days 208
humans dogs
x
x
x
x x x x x
Number of 2ck bites -‐ T
2014 -‐ 111,677 dogs in NB -‐ 6,700 (6%) Borrelia seroposiHve
Ipsos-‐Forward on behalf of the Canadian Animal Health InsHtute (h3p://www.cahi-‐icsa.ca/companion-‐animal-‐health/ and StaHsHcs Canada
To produce 6,700 Borrelia seroposiHve dogs with a Hck infecHon rate of 12.3% and with 60% fed 3+ days gives an esHmated 90,786 2ck bites
Adjustments: Average 1.33 Hcks/dogs (so more Hck bites) Not all Hcks found by dog owners (so more Hck bites) Tick infecHon rate can reflect infecHon acquired from host so infecHon rate could really be 11.56% – so more Hck bites
Part 1. Dogs
Part 2. Extrapola2ng dog to human 2ck bites:
Number of 2ck bites -‐ T
To what extent does a Hck prefer a dog to a human?
This can be esHmated from return rates from passive surveillance programmes or from the literature.
h3p://www.feathersandfleece.com/gpage13.htmlfgfr
NB Hcks from humans NB Hcks from dogs Dibernardo et al (2014) 123 187 Lewis and Lloyd (in prep) 25 429
148 616
19.4% of Hcks on humans vs dogs Lindenmeyer et al 1991 :human:dog Hck raHo of 1:6 (14.3%)
This gives us an esHmate of 19.4% x 90786 dog Hck bites 17,612 human 2ck bites (T).
So what does this mean for humans?
Lindenmeyer et al 1991 6,475 humans with Lyme
5 New Brunswick Public Health
LB = I x F x T(h) MulHplied by the infecHon rate (I) of 12.3% and probability of a Hck on a human having fed 3+ days (F), 8%
173 predicted human infecHons in NB in 2014. (ConservaHve esHmate)
Discrepancies: TesHng at the Hme of Hck bite Lyme diagnosis not considered Under-‐reporHng Single Her vs two Hered tesHng SensiHvity of tesHng Perdurance of canine seroposiHvity
IDEXX tech notes
Conclusions
Canine seroposi2vity surveillance is a powerful complement to 2ck surveillance approaches • Inexpensive (as it is already
being done)
• Standardized methodologies
• NaHonal infrastructure in place
• Directly relevant to humans
• InsensiHve to problems with Hck endemnicity