Myths on CWDDebunking

CWD is closely related to mad-cow disease, which was found to infect humans in 1996. However,sinceCWDfirstwasdiscoveredin1967,therehavebeennoknownreportsofCWDinfectinghumans. WhilenolinkbetweenCWDandhumanillnesshasbeenidentified,theCentersforDiseaseControlandPrevention(CDC)andtheWorldHealthOrganization(WHO)advisepeopletoavoidexposuretoCWD-infected meat. TheCDCstates,“someanimalstudiessuggestCWDposesarisktocertaintypesofnon-humanprimates,likemonkeys,thateatmeatfromCWD-infectedanimalsorcomeincontactwithbrainorbodyfluidsfrominfecteddeerorelk.Thesestudiesraiseconcernsthattheremayalsobearisktopeople.” TheGameCommissionrecommendshunterswhoharvestdeerinDiseaseManagementAreas(DMAs)takeadvantageofthefreeCWD-testingofferedwithintheDMA.It’simportanttonotethisisnotafoodsafetytest.FailuretofindprionsintheexaminedtissuedoesnotindicatetheharvestedanimalisCWD-free. ButthetestsarevaluableinidentifyingCWD-positiveanimalsthatshouldnotbeconsumed.

MYTH: CWD Can infect humans.

MYTH: CWD has always been in Pennsylvania; the Game Commission just didn’t find it until recently. WhileitispossibleCWDhasalongerhistoryinPennsylvaniathanisknown,thedistributionofCWDinother states, as well as in Pennsylvania, suggests otherwise. Likeawildfire,CWDstartswithasinglespark,orsingleinfecteddeer,andslowlygrowsoutwardradiallyintoafire.Asthisfiregrowslarger,itmovesacrossthelandscape,burninghottestnearitscore.Similarly,CWDcasesconcentratenearthefirstinfectionandradiateoutwardasdeerencounteroneanother. Justlikeawildfire,sparkscanleapintonewareas,startingfiresnearby. ButnewcasesofCWDcanleapmuchgreaterdistanceswhenpeopletransportdeerordeercarcassesfromCWD-infectedareastouninfectedareas. TakePennsylvaniaforexample.TheGameCommissionbeganmonitoringCWDin2002,butthediseasewasn’tdetecteduntil2012,firstincaptivedeer,theninwilddeer.Over34,000wilddeerweretestedpriortothefirstdetection. ThefirstwildcasesofCWDin

PennsylvaniaweredetectedinthreedeerinBedfordandBlair

counties.Sincethen,CWD-positivewilddeerhavebeen

detectedinnineofPennsylvania’s67counties.

However,overhalfofPennsylvania’swildpositives

havebeendetectedinBedfordandBlaircounties.

IfCWDalwayswasinPennsylvania,wewouldexpectmorecasestobefoundstate-

wide, not solely in isolated areas. Asimilarpatternofinfection

appears in other states.

CWDPositiveLocations

This maps shows the location of each wild deer that has tested positive for CWD in Pennsylvania as of June 2019.

StudiesshowthatdeerpopulationswithhighprevalenceofCWDhavelowersurvivalrates,resultinginannualpopulationdeclines. EventhoughCWDhasalowprevalencenationwide,CWDshouldnotbedismissedasinsignificant.CWDalwaysisfataltothedeerandelkitinfectsand,unfortunately,thereisnocureorvaccineyet.

MYTH: EHD is a bigger threat to our deer herd.

MYTH: CWD does not kill deer.

MYTH: There is nothing a state can do about CWD other than let nature take its course.MYTH: Some deer are resistant to CWD. AlldeercanbecomeinfectedwithCWD,however,recentstudiesshowthatcertaingenotypescanmakeadeermoreorlesssusceptibletoCWD. Eventhosedeerwiththeless-susceptiblegenotypearenotimmunetoCWD,thoughtheyhavebeenfoundtolivemonthslongerthanotherinfecteddeer. Unfortunately,thisalsomeansdeerwiththeless-susceptiblegenotypecanspreadCWDforalongerperiod. MoreresearchisneededtofullyunderstandthesegenotypesandhowtheyaffectthespreadofCWD.

OutofthemillionsofdeerthathavebeentestedforCWDnationwide,lessthan2percenthavetestedpositive. ManypeopleusethisstatisticasgroundstojustifyaperceptionthatCWDisnotseriousthreattothedeerherd.Butthestatistic,whiletrue,ismisleadingbecauseCWD,likeotherdiseases,doesnotevenlydistributeitselfacrossthenation,orevenwithinstatesthemselves. Todate,CWDhasbeenfoundin26statesandthreeCanadianprovinces,andprevalencevarieswithineachstate.Aswithmostdiseases,theprevalenceinagivenareaincreaseswithtime.AreasinWyomingandColoradowhereCWDfirstwasfoundreportprevalencelevelsupwardof30percent,whilesomecountiesinsouthernColoradohaveyettodetectCWD. CWDprevalencealsovarieswithinourownstate,withthemajorityofCWDdetectionsoccurringinDiseaseManagementArea(DMA)2.CWDprevalencealsovarieswithintheDMAsthemselves.

MYTH: CWD is not a common disease in the U.S. and therefore is not a threat.

StudiesshowthatdeerpopulationswithhighprevalenceofCWDhavelowersurvivalrates,resultinginannualpopulationdeclines. EventhoughCWDhasalowprevalencenationwide,CWDshouldnotbedismissedasinsignificant.CWDalwaysisfataltothedeerandelkitinfectsand,unfortunately,thereisnocureorvaccineyet.

MYTH: EHD is a bigger threat to our deer herd.

MYTH: CWD does not kill deer.

MYTH: There is nothing a state can do about CWD other than let nature take its course.MYTH: Some deer are resistant to CWD.

ItistruethatEpizooticHemorrhagicDisease(EHD)canhavesignificantimpactsondeerpopulationslocallywherethediseasehits.ButCWDhasthepotentialtoreachfartherandbecomeamore-permanentproblem. EHDisavirusthatisspreadbytinybitingmidges,or“no-see-ums.”Pennsylvaniaonlyhasbeenimpactedaboutonceeveryfiveyears,withoutbreaksoccurringoversmallareasduringthesummer.Themidgesthendieoffafterthefirsthardfrost. EventhoughEHDquicklycankilllargenumbersofdeer,itisnotalwaysfatal.ManydeerthatcontractEHDsurviveanddevelopresistancetothedisease.EveninthoseareaswhereEHDcauseslargedeerdie-offs,thoselocalpopulationscanreboundquickly. OneofthemostdangerousthingsaboutCWDisthatitseffectsarenoteasilyvisible. Instead,CWDpicksatapopulation,onedeeratatime.Then,overtime,thediseasetakesanincreasingnumberofdeer. Duetoitsslow-movingnature,itcantakeyearsforCWDtobeginnegativelyaffectingdeerpopulations.However,nomatterhowslowCWDmoves,CWDalwaysisfatal.Itseffectsarereal. CWDcanbespreadbydeer-to-deercontactorindirectlythroughcontaminatedenvironments.Andonceintheenvironment,CWDcanremaininfectiousforseveralyears. Becauseofthisenvironmentalcontamination,onceCWDisestablishedinanarea,it’snearlyimpossibletoeradicateandwillcontinuetoinfectdeerforyears.

AlldeercanbecomeinfectedwithCWD,however,recentstudiesshowthatcertaingenotypescanmakeadeermoreorlesssusceptibletoCWD. Eventhosedeerwiththeless-susceptiblegenotypearenotimmunetoCWD,thoughtheyhavebeenfoundtolivemonthslongerthanotherinfecteddeer. Unfortunately,thisalsomeansdeerwiththeless-susceptiblegenotypecanspreadCWDforalongerperiod. MoreresearchisneededtofullyunderstandthesegenotypesandhowtheyaffectthespreadofCWD.

OutofthemillionsofdeerthathavebeentestedforCWDnationwide,lessthan2percenthavetestedpositive. ManypeopleusethisstatisticasgroundstojustifyaperceptionthatCWDisnotseriousthreattothedeerherd.Butthestatistic,whiletrue,ismisleadingbecauseCWD,likeotherdiseases,doesnotevenlydistributeitselfacrossthenation,orevenwithinstatesthemselves. Todate,CWDhasbeenfoundin26statesandthreeCanadianprovinces,andprevalencevarieswithineachstate.Aswithmostdiseases,theprevalenceinagivenareaincreaseswithtime.AreasinWyomingandColoradowhereCWDfirstwasfoundreportprevalencelevelsupwardof30percent,whilesomecountiesinsouthernColoradohaveyettodetectCWD. CWDprevalencealsovarieswithinourownstate,withthemajorityofCWDdetectionsoccurringinDiseaseManagementArea(DMA)2.CWDprevalencealsovarieswithintheDMAsthemselves.

MYTH: CWD is not a common disease in the U.S. and therefore is not a threat.

Ifyoucan’tseeit,itdoesn’texist–right? DespitedecadesofresearchonCWD,manypeoplebelieveCWDisn’tathreat,simplybecausetheycan’tseeit. WiththecurrentlowprevalenceofCWDstatewide,it’sunlikelyforanyonetoseeCWD-positivedeerdisplayingsymptoms,letalonewatchaCWD-positivedeerdie.WhetheryoucanseeCWDornot,CWDisaserious threat to Pennsylvania’s deer herd. AsCWDslowlyprogressesinthebody,itcreatesholesinthebrain,oftencausinginfecteddeertobecomemoresusceptibletootherthreats.Therefore,infecteddeeroftendiefromcauseslikehunting,predation,orvehiclecollisions,beforeoutwardsignsofthediseaseareapparent.

ThereisnoevidencethatshowsCWDwilldissipatenaturally. Unfortunately,optionsarelimitedwhenitcomestomanagingCWD.However,increasedhunterharvestandtargetedremovals(culling)hasprovedeffectiveinotherstates.NewYorkdetectedtwowildcasesofCWDin2005,justafterCWDwasdetectedatanearbycaptivedeerfacility.Withinweeks,deermanagersusedacombinationofhunterharvestandcullingtoreducedeerpopulationsinthelocalarea. NomoreCWDcaseshavebeenfoundinthestatesince.

StudieslookingattheaveragesurvivalratesofCWD-infecteddeer,showthatdeercandiesolely

fromCWD.NottomentionthatstudieshavefoundthatCWD-infecteddeeraretwotofourtimesmorelikelytodieannuallythannon-infecteddeer.AndwhetheraCWD-infecteddeerdiesdirectlyfromdiseaseoritgetshitbyacarfirst,CWDlikelyis

contributingtothatanimals’death.

AsthenumberofdeerwithCWDincreases,deer-populationdeclineswillfollow,andasaresult

huntingopportunitycouldbereduced.

NewYork’ssuccessstory,alongwithexperiencesfromotherstates,provideshopethatincreasedhunterharvestandtargetedremovals,ifconductedquicklyandeffectivelyafterCWDisdetectedinanewarea,canbeusedtocombatCWD. Illinoisalsobegancullingeffortsin2003,soonafterCWDwasdetectedinthestate.IllinoishasbeenabletoholdCWDatbay,maintainingalowCWDprevalence,usingincreasedhunterharvestandtargetedremovalsaroundknownCWD-positives.WisconsinalsodetectedCWDin2002andutilizedhunterharvestandtargetedremovalsofdeerin2003,butduetopublicpushback,targetedremovaleffortsendedin2007.CWDhasspreadandincreasedinthestatesince,withsomeareasshowing50percentofadultbucksbeinginfected. Whilereducingdeerpopulationsoftenisopposedbyhuntersandwildlifeenthusiastswhoenjoyseeinglargenumbersofdeer,itiscurrentlythebestmanagementstrategyknowntoslowthespreadofCWD. ThequestioniswouldyouratherreducedeernumbersinhopesofmanagingCWDordonothingandwatchCWDspread?

Graph shows how different management actions can impact CWD prevalence overtime. Disclaimer: Graph compares CWD prevalence only in CWD-positive areas in each state, not CWD prevalence state-wide.

MYTH: The Game Commission plans on killing all the deer to manage CWD. WithnoknowncureforCWD,optionstomanagethediseasearelimited. Todate,reducinglocaldeerpopulationsistheonlymanagementstrategythathasshownanysuccessatstablizingorreducingCWDprevalence.ReducingdeernumbersaroundnewCWDdetectionslowersdiseasetransmissionthroughreduceddeercontactandreducesthenumberofprionsshedontotheenvironment. TheGameCommissionwantshunterstohavethefirstopportunitytoharvestdeerasameanstomanageCWD.Whilethemanagementactionsproposedinthe2020draftCWDResponsePlanincreasehunteropportunitiestoharvestdeerinCWD-positiveareas,theobjectiveisnottoremoveallthedeerfromthese areas. Illinoishasutilizedsimilarmanagementstrategies--proposedinthe2020draftCWDResponsePlan--tocontrolCWDforover16years.Despiteincreasedhuntingopportunitiesandtargetedremovals,thenumberofdeerharvestedbyhuntershasnotdroppeddrastically.Withhuntersharvesting159,550deerduringthe2002-2003huntingseasonand151,709deerduringthe2018-2019huntingseason.

Formoreinformationcall1-833-infocwdoremailinfocwd.pa.gov