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The re-emergence of canine leptospirosis in Ontario
John F Prescott,Department of Pathobiology,
University of Guelph
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Leptospirosis concepts
• A zoonotic disease caused by the spirochete Leptospira
• Home is kidney, often shed in urine for life in maintenance hosts
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Serovars and maintenance hosts of pathogenic leptospires in Canada
Serovar Maintenance hostbratislava Pigs (horses, dogs)canicola Dogsgrippotyphosa Raccoons, skunks, voleshardjo Cattle, sheepicterohaemorrhagiae Ratspomona Pigs, skunks, cattle,
raccoons?
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Leptospirosis: epidemiology
• Contact with maintenance (reservoir) host or its urine causes infection in incidental hosts
• Leptospires are fastidious• Survive optimally where wet and moderate
temperatures (fall), about 6 weeks
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0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6 7 8 9 1 0 1 1 1 2Month
Num
ber o
f Cas
es
Positive Suspic ious
Number of serologically positive and negative canine leptospira cases, year 2000, AHL
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Historical background: leptospirosis in dogs• Maintenance host of canicola• Infections in children in 1970s• No longer reported in in United States or
Canada• Icterohaemorrhagiae, incidental infection,
rat derived, rare disease • Controlled by routine vaccination
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Annual prevalence of leptospirosis/100,000 dogs at 22 veterinary teaching hospitals in USA and Canada
0
50
100
150
200
250
1970 1973 1976 1979 1982 1985 1988 1991 1994 1997
Cases
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Leptospirosis in dogs: emergence of the new serovars
• Increasing reports since 1990 of grippotyphosa, pomona in United States and Canada
• Dramatic increase in eastern Canada
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Annual submission of serum samples to AHL for canine leptospirosis, positive and negative for the MAT, 1998 to
2006
0
50
100
150
200
250
300
350
1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
Cou
nts Negative
Positive
Alton et al (2009)
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03 6 5
1912
3429
21
37
22
0
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40
Posi
tive
case
s
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
MAPAQVitatech
It’s an urban- suburban disease of dogs
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Why has leptospirosis in dogs increased?
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Why has leptospirosis in dogs increased?
• Increase in infection in wildlife vectors (raccoons, skunks) in urban, suburban areas
• Climatic factors (impact on vector, survival)• Awareness by vets
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Raccoon populations
100 raccoons per square kilometer suburban Toronto
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Global Climate Change
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Northern Mocking Bird: Toronto Christmas Bird Count
0
5
10
15
20
25
30
1990 1992 1994 1996 1998 2000 2002 2004
Number
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Awareness by vets?Regression line showing linear increase in the proportion of positive tested dogs, Cochran- Armitage trend test
Alton et al., 2009
Genuine increase, not just “awareness”
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Canine leptospirosis
• Typically acute renal failure • Sometimes hepatitis• Other, various
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Copyright ©2008 Canadian Medical Association or its licensors
Brown, K. et al. CMAJ 2008;178:399-401
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Human infections
• Anecdotally 6-8 infections acquired from dogs in Ontario and Quebec in last few years
• Have involved DVMs, AHTs, and owners• Some very delayed diagnosis
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Disease in humans
• “Biphasic”: acute phase, immune phase • Most mild or subclinical• Recognized cases: acute onset fever, chills
severe headache, myalgia, abdominal pain, conjunctival suffusion
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Disease in humans
• Aseptic meningitis < 25% • Severe: generally similar to dogs, more
emphasis on endotoxic, vascular damage effect
• Chronic: uveitis, persistent headaches, chronic hepatitis
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Current state of canine leptospirosis?
• Appears to be leveling off or declining• Effect of vaccination with “new” serovars?• Work to be done on seroprevalence,
shedding by dogs, vectors, human exposure, public education
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Acknowledgements
• Bev McEwen, Davor Ojkic, AHL• Gillian Alton, Olaf Berke, Richard Reid-
Smith, Population Medicine• Pet Trust• Wyeth Animal Health