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West Nile virus on the Prairies. Tasha Epp, DVM, PhD October 5, 2010. WNV 1999, New York. Spread across USA - 1999. Spread across USA - 2000. Spread across USA - 2001. Spread across USA – 2002. Spread across USA - 2003. Great Plains and WNv. Birds and WNv. Virus. Family: Flaviviridae

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West nile virus on the prairies

West Nile virus on the Prairies

Tasha Epp, DVM, PhD

October 5, 2010










Virus
Virus

  • Family: Flaviviridae

  • Genus: Flavivirus Japanese Encephalitis Antigenic complex

    • Includes JE, WNV, Kunjin, Murray Valley encephalitis, SLE, etc

    • RNA, single stranded



Species affected
Species affected

  • Birds

  • Mosquitoes

  • Humans, horses

  • alpacas, camels, sheep, squirrels, reptiles, etc


Clinical disease
Clinical Disease

  • Humans

    • Asymptomatic

    • WNV Fever

    • WNV neuro-invasive

  • Other mammals or birds

    • Neurological symptoms (mild to severe)

    • Death


Long term outcomes humans
Long Term Outcomes - Humans

  • Symptoms reported “post-recovery”

    • Self-reported fatigue

    • Memory problems

    • Extremity weakness

    • Word-finding difficulty

    • Headaches

    • Depression

    • Attention deficits


Surveillance in prairies from 2002 2010
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



Five hills health region
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)


Present surveillance in sk
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


Occupational data
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


Precautions for workers
Precautions for workers

http://www.cdc.gov/niosh/docs/2005-155/

http://www.phac-aspc.gc.ca/ols-bsl/wnvbio-eng.php


Control measures
Control Measures:

  • Source reduction

    • Remove standing water, etc

  • Mosquito control

    • Personnel protection

    • Larviciding

    • Adulticiding

  • Vaccination

  • Behavior modification


Mosquito control
Mosquito Control

  • Preferred method for surveillance in SK

  • Best prevention of infection in people?


Vaccination
Vaccination?

  • Is this feasible?

  • Who would get vaccinated?

  • Cost-benefit analysis?


Human behavior
Human Behavior?

  • DEET

  • Drain

  • Dress

  • Dusk to dawn


Northern colorado study
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


West nile virus on the prairies

Northern Colorado study

  • Loveland had higher neuro-invasive disease rate

    • Loveland = 38.6/100,000

    • Fort Collins = 15.9/100,000


Northern colorado study1
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


First nations and wnv
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)


Communicating risk
Communicating Risk

  • When?

  • How?

  • What?


Future of wnv
Future of WNv

  • What should we expect?

  • Is WNv here to stay?

  • Can we predict WNv years before they occur?