West Nile virus on the Prairies

1. West Nile virus on the Prairies Tasha Epp, DVM, PhD October 5, 2010

2. WNV 1999, New York

4. Spread across USA - 1999

5. Spread across USA - 2000

6. Spread across USA - 2001

7. Spread across USA – 2002

8. Spread across USA - 2003

9. Great Plains and WNv

10. Birds and WNv

11. Virus • Family: Flaviviridae • Genus: Flavivirus Japanese Encephalitis Antigenic complex • Includes JE, WNV, Kunjin, Murray Valley encephalitis, SLE, etc • RNA, single stranded

12. Natural Cycle

13. Species affected • Birds • Mosquitoes • Humans, horses • alpacas, camels, sheep, squirrels, reptiles, etc

14. Clinical Disease • Humans • Asymptomatic • WNV Fever • WNV neuro-invasive • Other mammals or birds • Neurological symptoms (mild to severe) • Death

15. Long Term Outcomes - Humans • Symptoms reported “post-recovery” • Self-reported fatigue • Memory problems • Extremity weakness • Word-finding difficulty • Headaches • Depression • Attention deficits

16. Surveillance in Prairies from 2002-2010 • 2002 • Humans, horses and birds in Manitoba • first bird and clinical horses reported in SK • 2003 • epidemic (birds, horses, humans, etc) in SK and MB • First cases in AB • 2004 – 2006 • Mild years, very few cases • 2007 • epidemic returns in full force on prairies • 2008-2010 • Few cases reported

17. 2003: Horse, bird, human and mosq.

18. Five Hills Health Region • Highest reported number of cases in SK • Seroprevalence • Overall 9.8% (7.4, 12.6) • Rural only 16.8% • Urban only 3.2% • Rural versus urban: • 6 times more likely to be positive (95% CI: 3, 13)

19. Present Surveillance in SK Regardless of the risk rating for your region, remember that there is no such thing as "risk-free". If you can be bitten by a mosquito, you can contract West Nile Virus. Source: Saskatchewan Ministry of Health, Population Health Branch

20. Occupational Data • Mosquito exposure • Rural residents or workers • Farmers • Outdoor jobs or recreation • Tissue or fluid exposure • Laboratory, field or clinical workers • People involved in dead bird collection • Veterinarians • Pathologists

21. Precautions for workers http://www.cdc.gov/niosh/docs/2005-155/ http://www.phac-aspc.gc.ca/ols-bsl/wnvbio-eng.php

22. Control Measures: • Source reduction • Remove standing water, etc • Mosquito control • Personnel protection • Larviciding • Adulticiding • Vaccination • Behavior modification

23. Mosquito Control • Preferred method for surveillance in SK • Best prevention of infection in people?

24. Vaccination? • Is this feasible? • Who would get vaccinated? • Cost-benefit analysis?

25. Human Behavior? • DEET • Drain • Dress • Dusk to dawn

26. Northern Colorado study • Loveland and Fort Collins • Similar ecology, demographics • High plains ecoregion • 90% white, around 10% >65 yrs • Loveland had mosquito control program • Less WNV-infected mosquitoes than Fort Collins

27. Northern Colorado study • Loveland had higher neuro-invasive disease rate • Loveland = 38.6/100,000 • Fort Collins = 15.9/100,000

28. Northern Colorado study • Loveland residents • reported less use of DEET • Most influenced by age • Second influenced by risk perception • more likely to spend time outdoors at dusk and dawn • both weekdays and weekends • Long clothes not important

29. First Nations and WNv • Identified many activities resulting in exposure • Identified features of homes or yards resulting in exposure • Control measures • Smoke or Mosquito coils • DEET based products • Clothing (children versus adults)

30. Communicating Risk • When? • How? • What?

31. Future of WNv • What should we expect? • Is WNv here to stay? • Can we predict WNv years before they occur?

32. Questions?