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Jul 8. Jul 28. Jun 14. May 19. Sept 13. > 6,000 carcasses; >3400 to lab ~ 550 WNV+ > 13,000 sightings. Time elapsed - pick-up of carcass to report of test result - 2002. Humans Quebec - 1 prob; 7 conf Ontario - 72 prob - 5 deaths; 48 conf - 1 death Alberta - 1 conf (US). Horses
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Jul 8 Jul 28 Jun 14 May 19 Sept 13 > 6,000 carcasses; >3400 to lab ~ 550 WNV+ > 13,000 sightings
Time elapsed - pick-up of carcass to report of test result - 2002
Humans Quebec - 1 prob; 7 conf Ontario - 72 prob - 5 deaths; 48 conf - 1 death Alberta - 1 conf (US) Horses Quebec - 2 Ontario - > 80 Manitoba - ~ 150 Saskatchewan - 10
New in 2002 Direct transmission bird-to-bird: crows, ?others - epidemiological implications - ? risk of human handling • WNV found in many organs/tissues • high titre in oronasal cavity & feces/urine in many bird spp.
New in 2002 Implications of WNV in wild & domestic animals >100 spp of wild & pet birds susceptible • sig. mortality in some • Mammals: squirrels, dog, wolf, reindeer, mountain goat etc. • Implications for wildlife populations, zoos, endangered species, handlers & rehabilitators, • veterinarians, laboratorians, animal/pet owners
New in 2002 • Recrudescent Endemic vs. Introduced Epidemic pattern • Does WNV overwinter in mosquitoes, ?birds/mammals, to emerge again in the spring, or does it need to be reintroduced annually, presumably by migratory birds? • Implications: • predictability of recurrence; climate, overwintering vectors • overwintering - earlier initiation of cycle, longer time for amplification - ?greater human risk • bird surveillance necessary/useful or not • mosquito surveillance necessary/useful or not • larvicide or not • public health message & public attitudes
New in 2002 Recrudescent WNV? Peel – May, 2002
WNV Surveillance 2003 Dead birds Testing, if done, may be provincial or local responsibility Issues: Utility of repeated testing in known WN virus-positive localities & dead bird sighting data VecTest: 20 minute test; ~$15; 85% sensitivity, 92% specificity on oropharyngeal swab – crows; ? Useful for local testing; ?reporting & communications; ?confirmation