传染病学英文版课件：Malaria 疟疾

Malaria疟疾Whatismalaria?Malariaisavector-borneinfectiousdiseasecausedbyprotozoanparasites.Itiswidespreadintropicalandsubtropicalregions,includingpartsoftheAmericas,Asia,andAfrica.HistoryofmalariaProbablyoccurredintheNileValleyandAsiaMinor3000-4000BCDescribedinancientGreece400BCCharlesLaveranin1880discoveredmalariaparasitesinhumanbloodRonaldRossin1897demonstratedthemosquitotransmissionofmalaria

“IhavefoundthysecretdeedOhmillionmurderingDeath.”

H.E.ShorttandP.C,C.Garnhamdiscoveredhypnozoitesin1948About4700yearsago,theChineseemperorHuang-Tiorderedthecompilationofamedicaltextbookthatcontainedalldiseasesknownatthetime.Inthisbook,malariaisdescribedingreatdetail-theearliestwrittenreportofthisdisease.CollectionoftheUniversityofHongkongMalariaFactSheet2.5billionpeopleatrisk300-500millioncaseseveryyear,withincreasingtendencyca.1milliondeathsperyearevery40secondsachilddiesfrommalariavariousfactorsleadtothepredictionthatthenumberofdiseasecaseswilldoubleoverthenexttwentyyears90%ofallmalariacasesoccurinAfricaintheendemicareasofAsiaorSouthAmerica,anaveragepersonisstungbyamalariavectorabout5timesayear.IncertainregionsofAfricathishappensover1000times!IncidenceEachyearMalariacauses200-300millioncasesItkillsover1millionpeopleeveryyearItiscausesbyaparasitecalledplasmodium(4types)Itisspreadbytheanophelesmosquito(72types)DistributionAtlowaltitudesDuringhotseasonsInplaceswheretheAnophelesmosquitoisabletobreedinfreshwaterWheretheenvironmentprovides–water,vegetation,temperatureSpread-TransmissionInorderfortransmissiontooccurseveralfactorsareinvolved:MosquitoHumansParasiteEnvironmentMosquito,HumansandEnvironmentUsually,peoplegetmalariabybeingbittenbyaninfectivefemaleAnophelesmosquito.

Transmissionofmalariacanhappenwhereverthetemperatureisbetween16and33℃,theairismoderatelyhumid,andthealtitudeislessthan2000mabovesealevelInfectioussporozoitesgetinjectedintotheskintogetherwithsalivaduringAnophelesbitePlasmodium-lifecycleMalariatransmittedbyfemaleAnopheles.Over60typesApicomplexagroupofprotozoa,havespecializedcomplexofapicalorganellesinvolvedinhostcellinvasion.Thelifecycleofmalariaparasites.Amosquitocausesaninfectionbyabite.First,sporozoitesenterthebloodstream,andmigratetotheliver.Theyinfectlivercells,wheretheymultiplyintomerozoites,rupturethelivercells,andreturntothebloodstream.Then,themerozoitesinfectredbloodcells,wheretheydevelopintoringforms,trophozoitesandschizontsthatinturnproducefurthermerozoites.Sexualformsarealsoproduced,which,iftakenupbyamosquito,willinfecttheinsectandcontinuethelifecycle.Thelifecycleofmalariaparasitesinthehumanbody.

MalariaPlasmodium

lifecycleSchizogony,occursinhuman,intermediatehost,haploidreplication.Exo-erythrocyticstageerythrocyticstageSporogony,occursinmosquitogut,diploidzygotesEtiologicagentsofhumanmalariaPlasmodiumfalciparumPlasmodiumvivaxPlasmodiumovalePlasmodiummalariaePathogenesisDestructionoferythrocytes;anemiaLiberationofparasiteanderythrocytesmaterialintocirculationHostreactiontotheseevents(multipleorgansystemdisease,acidosisinacutedisease)P.falciparumhasuniquesequestrationinmicrocirculationofvitalinterferingwithflowandtissuemetabolism.Long-termeffectsofrepeatedinfections-learningdeficit,spontaneousabortion,reducedgrowthrates;allmaybeduetoprolongedacidosisMicrographofaplacentafromastillbirthduetomaternalmalaria.H&Estain.Redbloodcellsareanuclear;blue/blackstaininginbrightredstructures(redbloodcells)indicateforeignnucleifromtheparasites.Adhesion:importantfortheparasiteand

animportantcauseofpathologyTheadhesionofinfectederythrocytestotheendotheliumofcapillariesisessentialforparasitesurvival,butitisalsoanimportantcauseofmalariapathologyThevarioushumanmalariasMalariaquartana:-Plasmodiummalariae-Feverattackswithaperiodicityof72h-goodprognosisexceptwhenkidneycomplicationsarise-riskofrelapseupto30yearsafterinfectionTypicalsymotomsofmalariaShivering(cold)30minutes~2h;Highfever2~6hheadache,bodyachelanguorGreatsweating,thepatientfeelsmuchbetter,thebodytemperaturereturnedtonormal.ThevarioushumanmalariasMalariatertiana:-PlasmodiumvivaxorP.ovale-Feverattackswithaperiodicityof48h-rarelyfatal-frequentrelapsesuptotwoyearsafterinfectionThevarioushumanmalariasMalariatropica:-Plasmodiumfalciparum-irregularfeverattacks-lifethreatening,particularlyforsmallchildrenbetween6monthsandfiveyear-noriskofrelapsesSignsandSymptomsChills

Fever–upanddownDehydrationAnaemiaJaundiceSignsandSymptomsHighfever(>40C)alternatingwithshiversAnaemiaandhypoferremiaDisruptionofliverfunctionsLacticacidosisHypoglycemiaDisruptionofplacentalfunctionsCerebralmalaria(predominantlyininfants)leadstoconvulsions,comaanddeathOpportunisticbacterialinfections?Blackwaterfever°inpatientswithG6PDdeficiencyEdemaofthelung-respiratoryproblemsKidneyfailureSevereMalariaPathogenesis:abilityofparasitetosequesterindeepvenousmicrovasculaturethroughprocessofcytoadherence.CerebralmalariaSevereAnemiaHemonaryEdema/ARDSCoagulationAbnormalitiesandThrombocytopeniaCardiovascularcollapseandshockSevereMalariaNephroticsyndrome,seeninP.malariae,youngchildrenproneHyperparasitemia:>5%RBCinfectedMetabolicacidosisHypoglycemia:esp.inpregnantfemaleseveninuncomplicatedmalaria,aftertreatmentwithQuinineHyperactivemalarialspleenomegalyMalariaDiagnosisClinicalDiagnosisMalariaBloodSmearFluorescentmicroscopyAntigenDetectionSerologyPolymeraseChainReactionClinicalDiagnosisHyperendemicandholoendemicareasLaboratoryresourcesnotneededFeverorhistoryoffeverSensitivityrangesfrompoortohighOftenhaspoorspecificityandpredictivevaluesOverlapwithothersyndromesMalariaBloodSmearRemainsthegoldstandardfordiagnosisGiemsastaindistinguishesbetweenspeciesandlifecyclestagesparasitemiaisquantifiableThresholdofdetectionthinfilm:100parasites/lthickfilm:5-20parasites/lRequirements:equipment,training,reagents,supervisionSimple,inexpensiveyetlabor-intensiveAccuracydependsonlaboratorianskillRecognizingMalariaParasitesInsidearedbloodcellOneormoreredchromatindotsBluecytoplasmRINGTROPHOZOITESCHIZONTGAMETOCYTEBlueCytoplasmRedChromatinBrownPigmentRecognizingErythrocyticStages:

SchematicMorphologyMalariaParasiteErythrocyticStagesRingformTrophozoiteSchizontGametocytesTreatmentofMalariaPrinciplesOfTreatment

Typeofinfection.Severityofinfection.Statusofthehost.Associatedconditions/diseases.Typeofinfection

Treatmentobviouslydependsonthetypeofinfection.PatientswithP.falciparummalariashouldbeevaluatedthoroughlyinviewofpotentialseriousnessofthediseaseandpossibilityofresistancetoantimalarialdrugs.

TypeofinfectionP.vivax:OnlyChloroquine25mg/kg+Primaquinefor14days.P.falciparum:Treatdependingonseverity&sensitivity.Primaquineasgametocytocidalisamusttopreventspread.Mixedinfections:BloodschizonticidesasforP.falciparumandPrimaquineasforP.vivax.SeverityofinfectionAllpatientswithmalariashouldbecarefullyandthoroughlyassessedforcomplicationsofmalaria.Acute,life-threateningcomplicationsoccuronlyinP.falciparummalaria.Malariaisprobablytheonlydiseaseofitskindthatcanbeeasilytreatedinjust3days,yetifthediagnosisandpropertreatmentaredelayed,itcankillthepatientveryquicklyandeasily.

Statusofthehost

Patient'sageandweightshouldberecordedsoastoadministeradequatedosesofantimalarialdrugsFunctionalcapacity-independent,dependent,bedriddenetc.Allpatientswithsevereprostrationandwhoarelookingillshouldbeadmittedtoahospitalandmonitored.StatusofthehostPatientswithnauseaandvomitingshouldbegivenantiemeticdrugstoensureadequatetreatment.Whilehigh-gradefeverfrequentlystimulatesvomiting,thismaybefurtheraggravatedbyantimalarialdrugs.Thereforeitisbettertoavoidadministrationoforalantimalarialsattheheightoffever.Onecanwaitforthefevertosubsidebeforetakingthedrugs.Ifthepatientvomitswithinonehouroftakingtheantimalarialdrugs,thesameshouldbere-administered.Incaseofpersistentvomiting,patientshouldbeadmittedandvomitingshouldbecontrolledwithparenteralantiemetics.Parenteralantimalarialsareneededonlyincasesofseveremalariaoruncontrolledvomiting.Adequatehydrationshouldbeensured.Associatedconditions/diseases

Pregnancy:Chloroquinecanbeusedsafelyinalltrimestersofpregnancy.Artemisininisnotshowntohaveanydeleteriouseffectsonthefetusinanimalstudiesandthereforecanbeconsideredifthesituationdemands.Quininecanbeusedinpregnancy,butoneshouldbewatchfulabouthypoglycemia.HowtoPreventMalaria?

HowcanIprotectmyselffromgettingmalaria?

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