tularemia in wild rodents and lagomorphs in canada gary wobeser, canadian cooperative wildlife...
Post on 18-Dec-2015
216 views
TRANSCRIPT
Tularemia in wild rodents and Tularemia in wild rodents and lagomorphs in Canadalagomorphs in Canada
Gary Wobeser, Canadian Gary Wobeser, Canadian Cooperative Wildlife Health Cooperative Wildlife Health
Centre, Department of Veterinary Centre, Department of Veterinary Pathology, U of Sask.Pathology, U of Sask.
““Few, if any zoonotic diseases have a Few, if any zoonotic diseases have a broader or more complex host broader or more complex host distribution and epizootiology” distribution and epizootiology” (Petersen & Schriefer, 2005)(Petersen & Schriefer, 2005)
1911 a “1911 a “plague-like diseaseplague-like disease” in ” in California ground squirrels California ground squirrels
1912 1912 Bacterium tularenseBacterium tularense isolated isolated
1914 human disease associated with 1914 human disease associated with cottontail rabbits (“rabbit fever”) and cottontail rabbits (“rabbit fever”) and later with deerfly bites (“deerfly fever) later with deerfly bites (“deerfly fever)
1929 human, Timmins, ON in association with 1929 human, Timmins, ON in association with snowshoe haressnowshoe hares
1930 sick snowshoe hare at Vavenby, BC 1930 sick snowshoe hare at Vavenby, BC 1931-1940 flurry of human cases in AB associated 1931-1940 flurry of human cases in AB associated with “rabbits” with “rabbits” 1938 F. tularensis1938 F. tularensis isolated from isolated from Dermacentor Dermacentor andersoniandersoni in AB in AB1940-42 domestic sheep in AB (2 human cases, 1940-42 domestic sheep in AB (2 human cases, jackrabbit, ground squirrel), many jackrabbit, ground squirrel), many D. andersoniD. andersoni1952-53 beaver and muskrat (Waterton Lakes 1952-53 beaver and muskrat (Waterton Lakes National Park, AB)National Park, AB)2005 outbreak in deer mice in SK2005 outbreak in deer mice in SK
Francisella tularensis (Francisella tularensis (4 4 subspecies):subspecies):
F. t. tularensisF. t. tularensis (type A tularemia)* (type A tularemia)*F. t. holarcticaF. t. holarctica (type B tularemia)* (type B tularemia)*F. t. mediaasiaticaF. t. mediaasiaticaF. t. novicidaF. t. novicida
two subtypes of two subtypes of F.t. tularensisF.t. tularensis : :A I (A east): lower elevations, eastern A I (A east): lower elevations, eastern cottontail rabbit, cottontail rabbit, Amblyoma americanumAmblyoma americanum, , D. D. variabilis variabilis high virulence (human)high virulence (human)A II (A west): higher elevations, Nuttall’s A II (A west): higher elevations, Nuttall’s cottontail??, cottontail??, D. andersoniD. andersoni, , Chrysops discalis , Chrysops discalis , very low virulence (human)very low virulence (human)
Generally accepted that:Generally accepted that:
Type A is Type A is associated with associated with lagomorphs and lagomorphs and tick or biting fly tick or biting fly transmissiontransmission
Type B is Type B is associated with associated with rodents and water rodents and water transmission but transmission but also occurs in also occurs in terrestrial terrestrial situationssituations
Sources of dataSources of data
CCWHC data baseCCWHC data base Records of veterinary colleges pre-Records of veterinary colleges pre-
CCWHCCCWHC Provincial veterinary laboratoriesProvincial veterinary laboratories Provincial and territorial wildlife disease Provincial and territorial wildlife disease
specialistsspecialists Published literaturePublished literature Public Health AgenciesPublic Health Agencies
Two types of dataTwo types of data
Cases diagnosed in wild rodents or Cases diagnosed in wild rodents or lagomorphs (retrospective IHC on lagomorphs (retrospective IHC on some suspect cases)some suspect cases)
Human cases in which an animal Human cases in which an animal source is describedsource is described
BCBC ABAB SKSK MMBB
OONN
QCQC NBNB NSNS PEPE NFNF NTNT YUYU
BeaverBeaver
MuskratMuskrat
Snowshoe hareSnowshoe hare
Richardson’s Richardson’s ground squirrelground squirrel
Deer mouseDeer mouse
House mouseHouse mouse
White-tailed White-tailed jackrabbitjackrabbit
Franklin’s ground Franklin’s ground squirrelsquirrel
MicrotusMicrotus spp. spp.
““rabbit”rabbit”
Diagnosed occurrence of tularemia in wild rodents and lagomorphs
BCBC ABAB SKSK MMBB
OONN
QCQC NBNB NSNS PEPE NFNF NTNT YUYU
BeaverBeaver
MuskratMuskrat
Snowshoe hareSnowshoe hare
GroundhogGroundhog
Ground squirrelGround squirrel
Deer mouseDeer mouse
Red squirrelRed squirrel
Microtus Microtus spp. spp.
Rodents on farmRodents on farm
““rabbit”rabbit”
““squirrel”squirrel”
Human disease associated with wild rodents/lagomorphs
Tularemia identified more Tularemia identified more commonly in beaver than in commonly in beaver than in muskrats or snowshoe hares, muskrats or snowshoe hares, but hares and muskrats are but hares and muskrats are
more common source of more common source of human infectionhuman infection
Beaver larger and more valuable, more likely to be submitted to laboratory
More people handle more muskrats and snowshoe hares
Tularemia in Canada is Tularemia in Canada is different than tularemia in different than tularemia in
USA?USA?
Human tularemia is a rare disease in Canada, Human tularemia is a rare disease in Canada, e.g., prior to 1970, 220 cases in Canada vs. e.g., prior to 1970, 220 cases in Canada vs. 33,089 cases in USA33,089 cases in USA
>90% of human cases in USA are tick->90% of human cases in USA are tick-transmitted; tick transmission to humans is rare in transmitted; tick transmission to humans is rare in CanadaCanadaDifferent “rabbits” are associated with tularemia
Snowshoe hare Eastern cottontail rabbit
White-tailed jackrabbit Nuttal’s cottontail rabbit
Snowshoe hares occur in Snowshoe hares occur in northern states and cottontails northern states and cottontails
occur in ON, QC, MB, SK, AB occur in ON, QC, MB, SK, AB and BC BUT:and BC BUT:
Tularemia very common in cottontails but Tularemia very common in cottontails but rare in snowshoe hares in USA rare in snowshoe hares in USA
Tularemia relatively common in snowshoe Tularemia relatively common in snowshoe hares in Canada but hares in Canada but nevernever diagnosed in diagnosed in cottontails in Canadacottontails in Canada
Human infection associated with Human infection associated with cottontails in USA but no record in Canadacottontails in USA but no record in Canada
Human infection commonly associated Human infection commonly associated with snowshoe hares in Canada, very with snowshoe hares in Canada, very rarely in USArarely in USA
QuestionsQuestions Why don’t we not see tularemia in cottontail rabbits Why don’t we not see tularemia in cottontail rabbits
or tick-transmitted disease in humans?or tick-transmitted disease in humans?
Where do various subspecies and subtypes of Where do various subspecies and subtypes of F. F. tularensistularensis occur in Canada? occur in Canada?
What are the reservoirs of terrestrial tularemia?What are the reservoirs of terrestrial tularemia?
What type of What type of F. tularensisF. tularensis occurs in snowshoe hares occurs in snowshoe hares and what effect does it have?and what effect does it have?
Why don’t we see tularemia in ground squirrels or Why don’t we see tularemia in ground squirrels or jackrabbits?jackrabbits?
ConclusionsConclusions
Tularemia is not a simple or a single Tularemia is not a simple or a single disease disease
Overlapping cycles of different Overlapping cycles of different subspecies and subtypes of subspecies and subtypes of F. F. tularensistularensis, different animals, various , different animals, various arthropods, waterarthropods, water
the true reservoirs are unknown the true reservoirs are unknown
““a challenge for the near future a challenge for the near future will be the unraveling will be the unraveling of the natural reservoirs of the natural reservoirs of Francisella tularensisof Francisella tularensis” ” (Tärnvik &Berglund, 2003)(Tärnvik &Berglund, 2003)