Equine Viral EncephalitisIowa State University：马病毒性脑炎爱荷华州立大学课件.ppt

1、Equine EncephalitidesSleeping SicknessEastern Equine Encephalitis(EEE)Western Equine Encephalitis(WEE)Venezuelan Equine Encephalitis(VEE)Overview Organism History Epidemiology Transmission Disease in Humans Disease in Animals Prevention and Control Actions to Take Center for Food Security and Public

2、 Health,Iowa State University,2011Equine Encephalitides Eastern equine encephalitis(EEE)Western equine encephalitis(WEE)Venezuelan equine encephalitis(VEE)Center for Food Security and Public Health,Iowa State University,2011THE ORGANISMThe Viruses EEE,WEE,and VEE viruses Family TogaviridaeGenus Alph

3、avirus Mosquito-borne DiseaseEncephalitis in humans and horsesOther mammals and birds are occasionally affectedCenter for Food Security and Public Health,Iowa State University,2011TRANSMISSIONTransmissionCenter for Food Security and Public Health,Iowa State University,2011Virus ParticlesDead End Hos

4、tsVertebrate HostsMosquito VectorMosquito Life Cycle Four-stage life cycle Egg,larva,pupa,adult Aedes species Lay single eggs Damp soil,later flooded Culex species 100-300 eggs in raft Lay eggs at night on water surface Survival requires wind protection Overwinter in egg stageCenter for Food Securit

5、y and Public Health,Iowa State University,2011Mosquito Life Cycle Larvae live upside down in water;“wriggler”Breathe via siphon tube Molt 4 times Pupal stage is restful,non-feeding;“tumbler”Breathe via“trumpets”Splits to allow adult to emergeCenter for Food Security and Public Health,Iowa State Univ

6、ersity,2011LarvaPupaMosquito Life Cycle Newly emerged adult rests Female takes blood mealOnly females biteAttractants for biting Carbon dioxide,temperature,moisture,smell,color,movement Mating occurs a few days after flight Lifespan varies from 4 to 30 daysCenter for Food Security and Public Health,

7、Iowa State University,2011Vectors of the Equine EncephalitidesDisease Mosquito VectorEEECuliseta melanuraAedes spp.Culex(Cx.)nigrapalpus Coquilletidia spp.WEECulex tarsalisAedes melanimonAedes dorsalisAedes campestrisVEECulex(Melanoconion)spp.Center for Food Security and Public Health,Iowa State Uni

8、versity,2011SUMMARY OF EQUINE ENCEPHALITIDESDistribution,Magnitude,and Outcomes Equine Encephalitides:Classification and DistributionDiseaseFamily,GenusDistributionEEETogaviridaeAlphavirusEastern U.S.WEETogaviridaeAlphavirusWestern U.S.VEETogaviridaeAlphavirusSouthern U.S.Center for Food Security an

9、d Public Health,Iowa State University,2011Human Risks and Outcomes Eastern equine encephalitisElderly most at riskCase fatality rate:33%Western equine encephalitisChildren 1 year most at riskCase fatality rate:3%Venezuelan equine encephalitisChildren most often affectedFatalities are rareCenter for

10、Food Security and Public Health,Iowa State University,2011Animal Risks and Outcomes Case-fatality rate in horsesEEE 90%VEE 50 to 90%WEE 30%Vaccine availablein the U.SCenter for Food Security and Public Health,Iowa State University,2011EASTERN EQUINE ENCEPHALITISEEE History 1831Unknown encephalomyeli

11、tis virus affects horses in Massachusetts 1933EEE first isolated from a horse 1937EEE identified in ring-necked pheasants 1938EEE first isolated from human brainCenter for Food Security and Public Health,Iowa State University,2011EEE History 1942-1943Michigan epidemic 1947Southern Louisiana and Texa

12、s14,000 cases83%case fatality rate 1951Isolated from Culiseta melanuraCenter for Food Security and Public Health,Iowa State University,2011EEE TransmissionCenter for Food Security and Public Health,Iowa State University,2011Culiseta melanuraPecking transmissionAedes spp.Coquilletidia perturbansDead

13、end hosts:Horses,humans,other mammalsBird migrationOver wintering?Spring ReintroductionSummerSwampy areasEEE Epidemiology 1964-2010270 cases total Average 6 cases each yearAverage 1 to 2 deaths each year Case-fatality ratesHuman:30 to 70%Equine:90%Equine cases usually appear firstServe as sentinels

14、for human diseaseCenter for Food Security and Public Health,Iowa State University,2011Center for Food Security and Public Health,Iowa State University,2011Eastern Equine Encephalitis Virus Neuroinvasive Disease Cases Reported by State,1964-2010 Center for Food Security and Public Health,Iowa State U

15、niversity,2011Eastern Equine Encephalitis Virus Neuroinvasive Disease*Cases Reported by Year,1964-2010*Neuroinvasive disease includes cases reported as encephalitis,meningoencephalitis,or meningitis.Reported U.S.equine casesof EEE,2003-2012Center for Food Security and Public Health,Iowa State Univer

16、sity,2011Distribution map of reported equine EEE cases,2012Center for Food Security and Public Health,Iowa State University,2011209 cases totalEEE in Humans Incubation period:4 to 10 daysMild disease uncommonFever,myalgia,headache,nausea,vomiting,abdominal pain,and photophobiaSeizure and coma in sev

17、ere cases Longer fever and flu-like symptoms before CNS signs results in a better outcomeCenter for Food Security and Public Health,Iowa State University,2011EEE in Humans Survival rates associated with ageHighest in young adults:70%Lower in children:60%Lowest in elderly:30%Recovery can result in pe

18、rmanent brain damage Diagnosis by serology Treatment is supportive careCenter for Food Security and Public Health,Iowa State University,2011EEE in Horses Incubation period:5 to 14 days Clinical signs in horsesFever,anorexia,depressionCNS signs Hypersensitivity,aimless wandering,head pressing,circlin

19、g,ataxia,paresis,paralysis Death may occur within days Asymptomatic or mild infections also occur Equine vaccine availableCenter for Food Security and Public Health,Iowa State University,2011EEE in Birds Asymptomatic in most bird species Clinical signsDepression,tremors,leg paralysis,somnolenceEmus,

20、ostriches Hemorrhagic enteritis,emesisDeath 24 hours after onset VaccinationSome birds are vaccinated for EEECenter for Food Security and Public Health,Iowa State University,2011Diagnosis Ante mortem:serologyVirus neutralizationHemagglutination inhibitionELISAComplement fixationVirus isolation Post

21、mortemVirus identified in tissues(brain)Immunohistochemistry,ELISA,RT-PCRCenter for Food Security and Public Health,Iowa State University,2011WESTERN EQUINE ENCEPHALITISWEE History 1930Isolated from horse brainCalifornia;50%case fatality rate 1933Aedes aegypti experimentally infected with WEE Virus

22、transmitted to guinea pigs Virus transmitted to horses(1936)1938Isolated from human brainCenter for Food Security and Public Health,Iowa State University,2011WEE History 1941Natural infection found in mosquito Culex tarsalis Epidemic in Canada and northern U.S.1942Culex tarsalis identified as the ve

23、ctor 1943Confirmed as mosquito-borne diseaseBirds identified as reservoir hostCenter for Food Security and Public Health,Iowa State University,2011WEE TransmissionCenter for Food Security and Public Health,Iowa State University,2011Dead-end hosts Horses,humansCulex tarsalis Primary VectorPrimary Ver

24、tebrate HostsHouse SparrowHouse FinchP.MyersSecondaryAmplifiersBlacktailJackrabbitPrairie DogB.LundriganP.MyersWEE TransmissionCenter for Food Security and Public Health,Iowa State University,2011StateVectorAvian hostMammalian HostCOCulex tarsalisHouse sparrow,Red-winged blackbird,MagpieBlacktail ja

25、ckrabbit,Kangaroo ratCACulex tarsalis Aedes melanimonHouse sparrow House finchBlacktail jackrabbit,Western gray squirrelTXCulex tarsalis,Cx.quinquefasciatusAedes vexansHouse sparrowBlacktail jackrabbit,Prairie dogNMAedes dorsalis,Ae.campestrisWEE Epidemiology Culex tarsalisHigh populations in mid-to

26、 late-summerEpidemics associatedwith cool,wet springWind can carry mosquitoes 800 miles in less than 24 hours Cases appear in June-August 639 cases since 19641989-1997:No human deathsCenter for Food Security and Public Health,Iowa State University,2011Center for Food Security and Public Health,Iowa

27、State University,2011Center for Food Security and Public Health,Iowa State University,2011WEE in the U.S.:1993-2002MMWR1993 1994 1995 1996 1997 1998 1999 2000 2001 2002210Reported CasesYearWEE in Humans Incubation:5 to 10 days Resembles EEE but usually asymptomatic or mild in adults Clinical signsSu

28、dden onset of fever,headache,nausea,vomiting,anorexia,malaiseCNS signs in children less than 1 year Altered mental status,weakness,irritability,stupor,comaCenter for Food Security and Public Health,Iowa State University,2011WEE in Humans PrognosisPoor for young clinical patientsCase-fatality rate:3

29、to 15%Death within one week of clinical onset Diagnosis difficult from blood,CSFPost mortem virus isolation from brain Treatment is supportive care Vaccine available for military personnel onlyCenter for Food Security and Public Health,Iowa State University,2011WEE in Animals AsymptomaticBlacktail j

30、ackrabbit,kangaroo rat,Western gray squirrel,prairie dog,birds Horses with clinical signsFever,depression,altered mentation,head pressing,ataxia,dysphagiaProgress to paralysis,convulsions,deathMortality rate 30%Center for Food Security and Public Health,Iowa State University,2011WEE in Animals Diagn

31、osisSerology Can differentiate EEE and WEE using the virus neutralization or ELISA testsPost mortem Immunohistochemistry,ELISA,RT-PCR Treatment is supportive care Vaccine availableCenter for Food Security and Public Health,Iowa State University,2011VENEZUELAN EQUINE ENCEPHALITISViral StrainsSubtypeC

32、yclePathogenicI-AI-BI-CEpizootic/EpidemicHighly virulent for equinesI-D III-E IIII-F IV V VIEnzootic/EndemicNot for horsesLimited cases in humansCenter for Food Security and Public Health,Iowa State University,2011VEE Viral Strains Epizootic/Epidemic I-A,I-B,and I-C Disease in humans and horses Tran

33、smission by many mosquito species Natural reservoir unknown Horses and donkeys act as amplifiers Enzootic/Endemic Disease in humans Transmission mainly by Culex(Melanoconion)species Natural reservoir is rodents living in swamps and forestsCenter for Food Security and Public Health,Iowa State Univers

34、ity,2011VEE History 1938Isolated from horse brain 1962-1964Outbreak in Venezuela 23,000 human cases 1967Outbreak in Colombia 220,000 human cases Over 67,000 horse deathsCenter for Food Security and Public Health,Iowa State University,2011VEE History 1969-1971Largest recorded outbreakCovered area fro

35、m Costa Rica to Rio Grande Valley in TexasThousands of human encephalitis casesOver 100,000 horses died 1995Venezuela and ColombiaOver 90,000 human casesCenter for Food Security and Public Health,Iowa State University,2011VEE Epizootic TransmissionCenter for Food Security and Public Health,Iowa Stat

36、e University,2011Primary Vector multiple mosquito species Dead-end hostsHumansVertebrate Host HorsesOther species naturally infected but not amplifiersVEE Enzootic TransmissionCenter for Food Security and Public Health,Iowa State University,2011Primary Vector Culex(Melanoconion)species Dead end host

37、sHumansVertebrate HostRodentsP.MyersVEE in Humans Incubation period:1 to 6 days Usually acute,mild,systemic disease Clinical signsFever,chills,headache,myalgiaCoughing,vomiting,diarrheaCNS signs Encephalitis occurs in 4%of children Less than 1%of symptomatic adults Death is rareCenter for Food Secur

38、ity and Public Health,Iowa State University,2011VEE in Humans Pregnant womenFetal encephalitis,placental damage,abortion/stillbirth,congenital disease DiagnosisPaired sera with rising titerELISA IgG or IgM TreatmentSupportive care No vaccine availableCenter for Food Security and Public Health,Iowa S

39、tate University,2011VEE in Horses Incubation period:1 to 5 days Horses most susceptibleFever,anorexia,depression,flaccid lips,droopy eyelids and ears,incoordination,and blindnessDeath 5 to 14 days after clinical onset Case-fatality rate:50 to 90%In utero transmission results in abortion,stillbirthCe

40、nter for Food Security and Public Health,Iowa State University,2011VEE in Animals Most domestic animals do not show clinical signs or amplify the virus ExperimentallyInfected rabbits and dogs die after inoculationLaboratory animals susceptible Act as sentinels Guinea pigs,mice,hamsters Enzootic stra

41、ins do not cause disease in animalsCenter for Food Security and Public Health,Iowa State University,2011VEE in Animals DiagnosisVirus isolation Serology Paired sera with rising titer ELISA IgG or IgM TreatmentSupportive care Vaccine available for horsesCenter for Food Security and Public Health,Iowa

42、 State University,2011VEE as a Biological Weapon Aerosolized VEE Human and equine disease occur simultaneously Flu-like symptoms in humans Possible neurological signs in horses Large number of cases in a given geographic areaCenter for Food Security and Public Health,Iowa State University,2011PREVEN

43、TION AND CONTROLManagement ofMosquito-Borne Diseases Source reduction Surveillance Biological control Chemical controlLarvicideAdulticide Educating the publicHow to protect themselvesCenter for Food Security and Public Health,Iowa State University,2011Source ReductionCenter for Food Security and Pub

44、lic Health,Iowa State University,2011 Mosquito habitatsMake unavailable or unsuitable for egg laying and larval development Minimize irrigationand lawn watering Punch holes in old tires Fill tree holes with cement Clean bird baths,outside waterers,fountainsSource Reduction Contd Drain or fill tempor

45、ary pools with dirt Keep swimming poolstreated and circulatingAvoid stagnant water Open marsh water managementConnect to deep waterhabitats and flood occasionallyFish accessCenter for Food Security and Public Health,Iowa State University,2011Surveillance Sentinel chicken flocks Blood test and ELISA

46、to monitor seroconversionCenter for Food Security and Public Health,Iowa State University,2011 Mosquito trapping and testing for viral presence Record keeping Weather data,mosquito larval populations,adult flight patternsBiological Control Predators,natural and introduced,to eat larvae and pupaeMosq

47、uito fish Gambusia affinis,G.holbrooki Fundulus spp.,Rivulus spp.,killifish Other agents have been usedbut are not readily available CopepodsCenter for Food Security and Public Health,Iowa State University,2011Chemical Control Essential when:Source reduction not effectiveSurveillance shows increased

48、 population of virus-carrying mosquitoes Requires properly trained personnel Larvicides,adulticides Toxic to many birds,fish,wildlife,aquatic invertebrates,honeybees Human exposure is uncommonCenter for Food Security and Public Health,Iowa State University,2011Chemical Control Federal Food Drug and

49、Cosmetic Act limits the quantity of adulticide used Due to wind drift onto agricultural crops Method used varies Type of target mosquito Type of targeted habitat Aerial spraying covers wide area Funding provided by state or local government Rarely federalCenter for Food Security and Public Health,Io

50、wa State University,2011Larvicides Use when source reduction and biological control not feasible More effective and target-specific Less controversial than adulticides Applied to smaller geographic areasLarvae concentrate in specific locationsCenter for Food Security and Public Health,Iowa State Uni