An Overview of Porcine Astrovirus

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AnOverviewofPorcine Astrovirus ExcerptedfromtheSwineHealthInformationCenterDiseaseSheetandedited byDr.BaileyArrudaandDr.KentSchwartz IowaStateUniversity KeyPoints Ͳ Furtherresearch isneededinallareasofthevirusinordertobetterunderstand,treat,andpreventit Ͳ AstVisapublichealthconcerninhumansasitisimplicatedinfoodborneandhaszoonoticpotential Ͳ PoAstVmayplayaroleinentericdisease,andhasbeen associatedwithneurologicaldisease

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Introduction Porcineastrovirus(PoAstV)isanonͲenvelopedRNAvirusbelongingtothefamilyAstroviridae.Therearefiverecognizedlineages(PoAstV1toPoAstV5),allof whichareknowntocirculateinswineherdsintheUnitedStates.

PoAstVisfoundworldwidewithvariableprevalenceamongherds.PoAstVshavebeendetectedbyPCRinbothdiseasedandhealthypigs.Theclinicalimplications ofdetectionofPoAstVinfecesornasalswabsarenotwellcharacterize.

MorbidityandMortality PrevalenceofPoAstVwithinandbetweenfarmsvariesconsiderably.DiagnostictestingofdiarrheicfecesfromthroughoutNorthAmericafoundPoAstVin61.7% ofsamples,20%ofwhichwerepositiveforPoAstValonewhiletheremainderofpositivesamplescontainedPoAstVandoneormore otherpotentiallypathogenic viruses(i.e.rotavirus,transmissiblegastroenteritisvirus,porcinecircovirusͲ2,orporcinehemagglutinatingencephalitisvirus). AreportfromCanadadetected PoAstV byRTͲPCRin80%ofhealthypigsattimeofslaughterformarket.

IntheU.S., pigswithPAstVͲassociatedneurologicaldiseaseweredocumentedinamultistateswineproductionsystemin2017.Samplesfromneurologiccases weresubmittedfortestingonthreeoccasionsovera9Ͳmonthperiod.AnaffectedsowfarmreportedacaseͲfatalityrateof100%,whiletwocommercialgrowͲ outfacilitiesreportedacaseͲfatalityrateof75%.InHungary,theindexfarmhadexperiencedepisodesofneurologicaldiseaseoveratwoͲyearperiod(2015Ͳ 2017).About30Ͳ40weanedpigs(1.5Ͳ2%ofthefarmpopulation)wereaffectedeachmonth.Aspikeincases(about80cases/month,4%offarmpopulation)was seenduringtheautumnmonths.

Transmission AmajorityofpublishedreportssupportthefecalͲoralrouteinPoAstVtransmission.However,furtherresearchisneededinordertodrawfirmconclusionsabout howPoAstVspreads .

Clinicalsigns AllPoAstVlineagescanbedetectedinthefecesofpigsbyPCR.Therole,ifany,thatoneormorelineagesofPoAstVplayinentericdiseaseisunsettled.Recently, PoAstV3hasbeenassociatedwithneurologicdiseaseinswine.Themostcommonlyreportedneurologicalsignsinthesecasesincludeataxia,parasis,paralysis, astasia,and/orknucklingoverontheforelimbs,commonlywithprogressiontolateralrecumbency.

Immunity PigsexperimentallyinfectedwithPoAstVshedinfectiousvirusintheirfecessevendayspostͲinfectionanddevelopedneutralizingantibodytiters14dayspostͲ infection.TherearenocommerciallyavailablePoAstVvaccines.AntigenicdiversityamongPoAstVstrainsinagivenlocationmayprovideachallengeforvaccine developmentanddiseaseprevention.

CleaningandDisinfection PoAstVretaineditsinfectivityinwateratpH4.0for3hours,butwhenexposedtopH3.0for3hoursinfectivitydecreasedtwoͲfold.InfectivityofAstVwhen exposedtochlorinedisplayed2.5LTRafter1hourcontacttime.

ZoonoticPotential AstVisapublichealthconcerninhumansasitisimplicatedinfoodborneillnessesandcansurviveingroundwater.ThezoonoticpotentialofAstVsisunclear; porcineͲhumanAstVrecombinantshavebeendocumentedandhumanͲtoͲpigtransmissionissuspected.AstVcausesdiarrheainhumaninfants,butzoonotic transmissionfrompigstohumanshasnotbeenreportedtodate.Theabilityofthevirustorapidlymutate,andthepotential forananimaltobecomecoͲinfected withtwodifferentstrains,setsthestageforarecombinationeventfromwhichazoonoticstraincouldemerge.Furtherresearch andinvestigationintothe pathogenesisofAstVandvaccinedevelopmentwouldbenefitbothveterinaryandhumanmedicine.

GapsinPreparedness MoreinformationisneededaboutPoAstVanditsroleasaswinepathogen.PoAstV3hasbeenstronglyassociatedwithneurological diseaseandoneormore PoAstVsmaycausegastrointestinaldisease.Humanzoonosisfrompigshasnotbeenreported,butthepotentialforcrossͲspecies transmissionexists.Vaccine developmentmaybebeneficialtoboththehumanandanimalmedicalcommunities.Investigationstobetterunderstandtheecology, epidemiology,andclinical implicationsofPoAstVsinswine,alongwithimproveddiagnostictools,areneededformoreeffectivediseasepreventionandmitigation.

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8/3/2018