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H3N2CanineInfluenzaForVeterinarians

Canineinfluenzavirus Canine influenza virus (CIV) is a type ofinfluenza A that is adapted to dogs. Influenza virusstrains arenamedbasedon their hemagglutinin (H)andneuraminidase(N)types.TherearetwodifferentCIVsinNorthAmerica. H3N8CIVwasfirstidentifiedinFloridaintheearly 2000s and was the result of adaptation of anequine influenza strain to dogs.1 This virus is stillpresentintheUSbuttheincidenceofdiseaseappearstoberelativelylow. H3N2 CIV is a more recently encounteredstrain in North America.2-5 It is believed to haveoriginatedinAsiaasaresultofdirecttransmissionofanavianH3N2virustodogs.CanineH3N2waslikelyintroducedtotheUSin2015throughimportationofdogsfromSouthKorea.IthasspreadwidelyintheUS,causingoutbreaksinmanyregions.

H3N2 CIV was first identified in Canada insouthwesternOntarioinlateDecember2017.

Colourized transmission electron micrograph depicting theultrastuctureofaninfluenzavirusparticle(PHIL10073)

Transmission Transmission of CIV, as for other influenzaviruses, involves direct contact between animals,short-distance aerosol transmission and indirecttransmission from contaminated fomites. Directcontactposesthehighestrisk.Humanscanpotentiallyactasfomitesthroughshort-termcarriageofCIVontheirbodiesorclothing,withsubsequentexposureofadog.

Infected dogs can start shedding CIV beforetheonsetofdisease(usually~24hbefore),soclinicallynormaldogscanbeasourceofinfection.SheddingofH3N2CIVhasnotbeenwell investigated,butH3N2CIV appears to have a relatively long period ofinfectivity.Astudyofashelteroutbreakshowedthatshedding most often stopped with 14d, yetintermittent positive PCR results were obtained insomedogsforupto24days.5Whetherthatreflectsintermittentshedding,prolonged low levelsheddingorre-exposureisdifficulttodiscern.

Directnose-to-nosecontactposesthehighestriskoftransmissionofcanineinfluenzavirus.

Clinicaldisease H3N2 influenza causes disease that isindistinguishable from other causes of canineinfectious respiratory disease complex (CIRDC, alsoreferredtoas“kennelcough”).Dogsofanyagecanbeaffected,althoughdiseaseismorelikelytobesevereinveryyoungandolddogs,aswellasbrachycephalicbreeds.

Coughing, sneezing, nasal discharge, oculardischarge,decreasedappetiteandfeverarethemainsigns.Feverisoftentransientandmaynotbepresentby the time of veterinary examination. Cough canpersistaftereliminationofactiveinfection,andcoughisnotagoodindicatorofriskofviralshedding.Mostdogsfullyrecoverwithin2-3weeks.

Complications are uncommon but the trueincidenceofseverediseaseassociatedwithH3N2CIVis not well understood. Secondary bacterialpneumonia is themainconcern.Fatal infectionsarerarebutcanoccur.Highorpersistentfever,increased

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respiratory rate and effort, anorexia and purulentnasaldischargeareindicatorsofmoreseverediseaseand/orsecondarybacterialinfection.

Brachycephalicdogbreedsareathigherriskofdevelopingmoresevereclinicaldiseaseifinfectedwithcanineinfluenzavirus.

Diagnosis DiagnosisusuallyinvolvesdetectionofCIVbyPCR from nasal swabs. Nasopharyngeal ororopharyngealswabscanalsobecollectedbutnasalswabsarepreferred.Ocularswabscanalsobetestedbut are lower yield. PCR testing can broadly detectinfluenza A or target specific influenza types (e.gH3N2). PCR testing detects viral shedding, and ishighestyieldearlyindisease.

PCRonnasalswabsisthepreferredmeansofdiagnosisofCIVindogs, butmust be used early in the course of infection duringperiodofactiveviralshedding.

Serologicaltestingcanbeperformedbutisoflimiteduseclinically.InareaswhereCIVhasnotbeenpresent,a single positive antibody titre is suggestive ofinfection in dogs that have not been previouslyvaccinated or traveled to a region where CIV ispresent. However, definitive diagnosis requiresdetection of a 4-fold increase in antibody titre in

samplescollected2-4weeksapart.Itispreferabletotesttheacuteandconvalescentsamplesatthesametime,soserologicaldiagnosisofCIV isretrospective.Virus isolation can also be performed but is lesscommon.

Treatment Therearenospecifictreatments.Supportivecare(e.g.coughsuppressants)shouldbeprovided,asneeded.AntibioticsarenotindicatedforCIVinfection,but occasionally may be needed if a secondarybacterial component develops, as is described inrecentrespiratoryinfectionguidelines.6

VaccinationCommercialvaccinesareavailable.Thesemay

beagainstH3N8orbothH3N8andH3N2.Vaccinationis not 100% effective but can reduce the risk andpotentially severity of infection. A minimum of 2dosesisrequired,2-4weeksapart.CIVvaccinationisanon-corevaccine7thatshouldbeconsideredbasedontheriskofexposureandtheriskofcomplicationsofinfection.

Infectioncontrolinveterinaryfacilities CIVishighlytransmissibleinveterinaryclinics,particularlyinareaswhereCIVisnew,becauseofthehightransmissibilityofthevirusandthenaïvecaninepopulation.Various exposure risks and sourcesmaybepresent,includingmixingofdogsinwaitingrooms,contamination of waiting room, examination andtreatment roomenvironments,aerosol transmissioninwardandtreatmentareasandindirecttransmissionthroughveterinarypersonnelorequipment. Control of CIV in veterinary clinics isdependentonpromptrecognitionofthepotentialforCIVanduseofenhanced infectioncontrolpractices,along with good adherence to general principles ofinfectioncontrol.è Frontofficestaffshouldflaganyacuterespiratory

diseasecasesatthetimeofappointmentbooking.Ownerscanbedirectedtocallfromtheirvehicleupon arrival or come into the clinic initiallywithouttheirdog.Thedogcanthenbeadmitteddirectlytoanexaminationroomorisolationareaandpersonnelcanstarttheappointmentwearingadditionalpersonalprotectiveequipment (gownor lab coat that will be used just for thatappointment, gloves). Routine use of mask andeye protection is not required, but should beconsidered in situations where someone’s facewillbeincloseproximitytoapotentiallyinfected

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dog, especially if the dog is coughing. In thatevent,gogglesandmask,orafaceshield,shouldbeused.

è Infected(orsuspected)casesshouldbehousedinan isolation area and handled with enhancedprecautions(asdescribedabove).

è Potentially contaminated items (e.g.stethoscopes)shouldbecleanedanddisinfectedafter use on a CIV suspect. Potentiallycontaminated consumable materials should bedisinfectedordiscarded.

è Routine disinfectants, used properly, willinactivateCIV.Promptandcarefuldisinfectionofpotentially contaminated environments isrequired.

è Veterinarypersonnelshouldpaycloseattentiontohandhygiene.Handsshouldbewashedoranalcohol-basedhandsanitizershouldbeusedafterpatientcontact(includingafterremovinggloves).Alcohol-basedhandsanitizerswilleffectivelyinactivateCIV.

Zoonoticpotential H3N2CIVisdifferentthanthecommonH3N2human (seasonal) influenza virus. There is currentlyno evidence that H3N2 CIV can infect people.However,thepotentialforhumaninfectioncannotbediscounted.Ofgreaterconcernisthepotentialforre-assortmentofhuman influenzaandCIV, ifadog (orperson)isinfectedwithbothstrainsatthesametime,asoccasionalinfectionsofdogswithhumanH3N2orH1N1 influenza viruses have been identified. Re-assortmentofinfluenzavirusesisofconcernbecauseitcanpotentiallyresultinavirusthatisreadilyabletoinfect people but is different enough from otherhuman influenza viruses that people have noimmunity from previous influenza infection orvaccination.

OtherspeciesH3N2 CIV can infect cats, but the incidence

appearstobelow.FerretsaresusceptibletoarangeoffluvirusesandarealsosusceptibletoH3N2CIV.

Reporting As of January 1, 2018,Ontario veterinariansand veterinary laboratories are required toimmediately report known or suspected infectionswith “novel influenza viruses” to their localMedicalOfficerofHealth.This includes influenzavirusesnotknown to be circulating in Ontario, which wouldincludeH3N2CIVatthistime.Whatistherisk?

TheriskofdiseasetothegeneralpopulationposedbyH3N2canineinfluenzavirusis:

HEALTHYADULTS/OLDERCHILDREN

Individualswithcompromised immunesystems(e.g.HIV/AIDS, transplant and cancer patients) aremoresusceptible to many kinds of infections, includingthose thatmay be transmitted by pets. Infants andyoungchildren(lessthan5yearsold)aremorelikelythanadultstoextensivelyhandleanimalsifgiventheopportunity, which may increase the potential fordisease transmission. Young children should besupervisedwhenplayingwithanimals, andanadultshouldensurethattheywashtheirhandsafterwards.Petsshouldnotbeallowedtolickbrokenskinoranyperson’sface.Forthesegroups,theriskofdiseaseposedbyH3N2canineinfluenzavirusislikely:

YOUNGCHILDREN/IMMUNOCOMPROMISED

Additionalinformation:Hanson JM et al. Nasal swabs to detect canineinfluenzavirus.Clinician’sBrief2016.

Center for Food Security and Public Health.Diseaseinformation–Influenza.

The Ohio State University. Disease prevention atcaninegroupsettings.

• Canine influenza (flu) information for dogowners(handout)

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Referencesandimagesources:1.CrawfordPC,etal.Transmissionofequineinfluenzavirustodogs.Science2005;310:482-485.2. Voorhees IEH, et al. Spread of Canine InfluenzaA(H3N2) Virus, United States. Emerging InfectiousDiseases2017;23.3. Sun H, et al. Zoonotic Risk, Pathogenesis, andTransmission of Avian-OriginH3N2Canine InfluenzaVirus.JVirology2017;91.4. JangH,etal.Seroprevalenceof three influenzaAviruses (H1N1, H3N2, and H3N8) in pet dogspresented to a veterinaryhospital inOhio. J Vet Sci(Suwŏn-si,Korea)2017;18:291-298.5. Newbury S, et al. Prolonged intermittent virusshedding during an outbreak of canine influenza AH3N2 virus infection in dogs in three Chicago areashelters:16cases(MarchtoMay2015).JAMVetMedAssoc2016;248:1022-1026.6.LappinMR,etal.AntimicrobialuseGuidelinesforTreatment of Respiratory TractDisease inDogs andCats:AntimicrobialGuidelinesWorkingGroupoftheInternational Society for Companion AnimalInfectious Diseases. J Vet Internal Medicine /American College of Veterinary Internal Medicine2017.7.FordRB,LarsonLJ,McClureKD,etal.2017AAHACanineVaccinationGuidelines.JAmAnimHospAssoc2017;53:243-251.8.JeoungH-Y,LimS-I,ShinB-H,etal.ANovelCanineInfluenzaH3N2VirusIsolatedfromCatsinanAnimalShelter.VetMicrobio2013:1-22.CDCPublicHealthImageLibraryhttp://phil.cdc.gov/phil/home.asp