West Nile virus on the West Nile virus on the PrairiesPrairies

Tasha Epp, DVM, PhDTasha Epp, DVM, PhD

October 5, 2010October 5, 2010

WNV 1999, New YorkWNV 1999, New York

Spread across USA - 1999Spread across USA - 1999

Spread across USA - 2000Spread across USA - 2000

Spread across USA - 2001Spread across USA - 2001

Spread across USA – 2002Spread across USA – 2002

Spread across USA - 2003Spread across USA - 2003

Great Plains and WNvGreat Plains and WNv

Birds and WNvBirds and WNv

VirusVirus

Family: FlaviviridaeFamily: Flaviviridae Genus: Flavivirus Japanese Encephalitis Genus: Flavivirus Japanese Encephalitis

Antigenic complexAntigenic complex– Includes JE, WNV, Kunjin, Murray Valley Includes JE, WNV, Kunjin, Murray Valley

encephalitis, SLE, etcencephalitis, SLE, etc– RNA, single strandedRNA, single stranded

Natural CycleNatural Cycle

Species affectedSpecies affected

BirdsBirds MosquitoesMosquitoes

Humans, horsesHumans, horses

alpacas, camels, alpacas, camels, sheep, squirrels, sheep, squirrels, reptiles, etcreptiles, etc

Clinical DiseaseClinical Disease

HumansHumans– Asymptomatic Asymptomatic – WNV FeverWNV Fever– WNV neuro-invasiveWNV neuro-invasive

Other mammals or birdsOther mammals or birds– Neurological symptoms (mild to severe)Neurological symptoms (mild to severe)– DeathDeath

Long Term Outcomes - HumansLong Term Outcomes - Humans

Symptoms reported “post-recovery”Symptoms reported “post-recovery”– Self-reported fatigueSelf-reported fatigue– Memory problemsMemory problems– Extremity weaknessExtremity weakness– Word-finding difficultyWord-finding difficulty– HeadachesHeadaches– DepressionDepression– Attention deficitsAttention deficits

Surveillance in Prairies from 2002-Surveillance in Prairies from 2002-20102010

2002 2002 – Humans, horses and birds in ManitobaHumans, horses and birds in Manitoba– first bird and clinical horses reported in SKfirst bird and clinical horses reported in SK

2003 2003 – epidemic (birds, horses, humans, etc) in SK and MBepidemic (birds, horses, humans, etc) in SK and MB– First cases in AB First cases in AB

2004 – 2006 2004 – 2006 – Mild years, very few casesMild years, very few cases

2007 2007 – epidemic returns in full force on prairiesepidemic returns in full force on prairies

2008-20102008-2010– Few cases reportedFew cases reported

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

Five Hills Health RegionFive Hills Health Region

Highest reported number of cases in SKHighest reported number of cases in SK SeroprevalenceSeroprevalence

– Overall 9.8% (7.4, 12.6)Overall 9.8% (7.4, 12.6)– Rural only 16.8%Rural only 16.8%– Urban only 3.2%Urban only 3.2%

Rural versus urban:Rural versus urban:– 6 times more likely to be positive (95% CI: 3, 6 times more likely to be positive (95% CI: 3,

13)13)

Present Surveillance in SKPresent 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

  Minimal

Few West Nile Virus mosquitoes present. Minimal risk does not mean no risk; take precautions against mosquito bites.

Low

WNV mosquito development. Take precautions against mosquito bites.

Moderate

The mosquito species that carries West Nile Virus has been recorded in numbers that warrant extra precautions.

High

WNV-positive mosquitoes identified in significant numbers. Precautions against mosquito bites should be taken at all times.

Occupational DataOccupational Data

Mosquito exposure Mosquito exposure – Rural residents or workers Rural residents or workers

FarmersFarmers Outdoor jobs or recreationOutdoor jobs or recreation

Tissue or fluid exposureTissue or fluid exposure– Laboratory, field or clinical workersLaboratory, field or clinical workers

People involved in dead bird collectionPeople involved in dead bird collection Veterinarians Veterinarians Pathologists Pathologists

Precautions for workersPrecautions for workers

Using an effective insect repellent helps prevent mosquito bites.Photograph courtesy of CDC/PHPPO/DPDE/CAB/PhotoServices.

 

Long-sleeved shirts, long pants, and socks will help prevent mosquito bites.Photograph courtesy of Joe Larson, USDA.

 

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

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

Control Measures:Control Measures:

Source reductionSource reduction– Remove standing water, etcRemove standing water, etc

Mosquito controlMosquito control– Personnel protectionPersonnel protection– LarvicidingLarviciding– AdulticidingAdulticiding

VaccinationVaccination Behavior modificationBehavior modification

Mosquito ControlMosquito Control

Preferred Preferred method for method for surveillance in surveillance in SKSK

Best prevention Best prevention of infection in of infection in people?people?

Vaccination?Vaccination?

Is this feasible?Is this feasible? Who would get vaccinated?Who would get vaccinated? Cost-benefit analysis?Cost-benefit analysis?

Human Behavior?Human Behavior?

DEETDEET DrainDrain DressDress Dusk to dawnDusk to dawn

Northern Colorado studyNorthern Colorado study

Loveland and Fort CollinsLoveland and Fort Collins Similar ecology, demographicsSimilar ecology, demographics

– High plains ecoregionHigh plains ecoregion– 90% white, around 10% >65 yrs90% white, around 10% >65 yrs

Loveland had mosquito control programLoveland had mosquito control program– Less WNV-infected mosquitoes than Fort Less WNV-infected mosquitoes than Fort

CollinsCollins

Loveland had higher neuro-Loveland had higher neuro-invasive disease rateinvasive disease rate– Loveland = 38.6/100,000Loveland = 38.6/100,000– Fort Collins = 15.9/100,000Fort Collins = 15.9/100,000

Northern Colorado studyNorthern Colorado study

Northern Colorado studyNorthern Colorado study

Loveland residents Loveland residents – reported less use of DEETreported less use of DEET

Most influenced by ageMost influenced by age Second influenced by risk perceptionSecond influenced by risk perception

– more likely to spend time outdoors at more likely to spend time outdoors at dusk and dawn dusk and dawn both weekdays and weekendsboth weekdays and weekends

– Long clothes not importantLong clothes not important

First Nations and WNvFirst Nations and WNv

Identified many activities resulting in Identified many activities resulting in exposureexposure

Identified features of homes or yards Identified features of homes or yards resulting in exposureresulting in exposure

Control measuresControl measures– Smoke or Mosquito coils Smoke or Mosquito coils – DEET based productsDEET based products– Clothing (children versus adults)Clothing (children versus adults)

Communicating RiskCommunicating Risk

When?When? How?How? What?What?

Future of WNvFuture of WNv

What should we expect?What should we expect?

Is WNv here to stay?Is WNv here to stay?

Can we predict WNv years before they Can we predict WNv years before they occur?occur?

Questions?Questions?