人体寄生虫学-schistosomiasis

Schistosomiasis1800millionsliveinendemicregion200millionsinfectedMortality2,800,0002ThreeclinicalimportantschistosomesSpeciesResidentLocationLesionoftissueDistribution

S.mansonimesentericrectalveinLiver,intestineAfricaSouthAmericaS.haematobiumperivesicalvenousplexusofthebladder,uretersandkidneysthroughthehemorrhoidalplexusUrinarybladderReproductiveorgansAfricaMiddleEastS.japonicum

Portal-mesentericveinLiver,intestineAsia3Matedworm

♂:1-2cm,flattenedandwhite♀:1.2-2.8cm,cylindricalanddust-color4S.mansoniworms:themalewormcarriesthefemaleinthe“gynecophoralcanal”5gutovarytestesinseriesoviductuterus67

Egg

Miracidium8Hatchingofmiracidiumfromegg:

water:lowosmoticpressure;

temperature:hatchingisinhibitedwhentemperatureislowerthan100Corhigherthan370C;

illumination:hatchingisinhibitedunderdark;9Cercaria

（尾蚴）Escapeofcercariafromsnail

10Sheddingofcercariafromsnail:

water:freshwater

temperature:200C~250C

illumination:11migratingthroughskinmigrationfromthelungtotheportalvein12Adult→Egg→

Miracidium→Sporocyst→Cercaria

→Adult

(successivegenerations)

OncomelaniaHumans,mammaliansSkin—lymphatic(blood)vessel—heart(lung)--mesentericartery--capillaries--portalvein(copulation)--superiormesentericvenules13

PathogenesisandSymptomology1.Cercaria:

cercarialdermatitis—Ⅰ&ⅣhypersensitivereactionItchyrash，erythema，transient2.Schistosomula&adults：inflammationoflungandvein,andasympyomatic14"Swimmer'sItch"or"RicePaddyItch"

Swimmer'sitch,duckitch,orcercarialdermatitis,isashort-term,immunereactionoccurringintheskinofpeoplethathavebeeninfectedbywater-bornetrematodeparasites.Symptoms—itchy,raisedpapules,commonlyoccurwithinhoursofinfectionanddonotgenerallylastmorethanaweek.Pathogen—Mostcasesarecausedbyparasitesthatusewaterfowlasthevertebratehost（avianschistosomes）.Theyaccidentallyinfecthumans,givingrisetomildlyitchyspotsontheskin.

15Liverofmouseinfected7weekswithS.japonicum3.*Eggs:granulomatousresponse(肉芽肿反应)oftheeggLiverandcolonarethetwo“victims”16

ovalgranuloma

eosinophilsplasmacellslymphocytesmacrophagesEgg:solubleeggantigen(SEA)

(eosinophilicgranuloma)17Chronicgranuloma:fibrosisofgranuloma

epithelioid→fibroblast→collagenousfiber

pipestem-fibrosis1819IntestinalimpairmentEggsofS.haematobiuminaurinarybladderbiopsyspecimen20Chronicschistosomiasis:GranulomatoushepatitisandcolonitisGranulomatoushepatitis：hepatomegalynotendernessGranulomatouscolonitis:intermittentabdominalpain,diarrhea,orgrume-bloodystool

Acuteschistosomiasis:

fever,cough,bloodysputum,abdominalpain,diarrhea,mucous-bloodystool…21AdvancedstageofschistosomiasisHepaticcirrhosis,portalhypertensionPortacavalcollateralcirculationsplenomegalyhepatomegalyascitesgrowthstuntinglesionofcolon，bladder22Theabdomenofan11-year-oldboywithintestinalschistosomiasiswiththesizeandextentoftheliverandspleenmarked.Hyperfunction,portalhypertension;hemorrhageofupperdigestivetract23Notetheascitesanddistensionofthecollateralveinsduetoportalhypertensionascites,portalhypertension,umbilicalhernia,imbalanceofliverfunctionalcompensation24Patientsuffersfrom

schistosomiasis,primarilyinfectedin199125abdominalpain;diarrhea;constipation;ileus26

S.mansoni+ S.mansoni

S.haematobium

bloodyurinesnoapparentsymptoms

hepatomegaly

27Urinaryschistosomiasis

(S.haematobium)CystoscopyXrayfilmofpelvicregionSymptomsarerelatedtochronicstagewhenpainlesshematuria,and/orcystitisareseenHydronephrosisandhydrourater,evendeathfromrenalfailurearesecondary2825year-oldmanwithadvancedschistosomiasisGrowthstunting29Severesyndromes:hemorrhageofupperdigestivetracthepaticcomaEctopiclesion:occupyingdamagecausedbymigrationofeggstobrainorlung…

30DiagnosisParasitology-detectionofeggsinexcreta.Insensitive(particularlyinlowinfectionintensity)Detectionofschistosome-specifichostantibodiesinbodyfluids.Sensitivebutantibodiesmaypersistafterinfectioniscleared(useofisotypes?)Detectionofparasiteantigensinbodyfluids&excreta.Insensitive(particularlyinlowinfectionintensity)

31S.japonicumEggsofschistosomesS.mansoniS.haematobium32Serodiagnosis

Indirecthaemagglutination:anold,butquickandsafetechnique33ELISA:frequentlyfavoured34Factorsofprevalence

andcontrol

FecesWater

SnailsHowtocontrol?SourceoftransmissionSusceptiblepopulationX35IntermediatehostofS.japonicum

—Oncomelania1cminsize;amphibian；nail-like;habitat:water,loosesoilandgrass36Biomphalariaspec.,avectorofschistosomiasisinAfrica

producingcercariae(fieldcollectedinMali).3738ChemotherapyPraziquantel

drugofchoiceSomeevidenceofsomeschistostrainstoleranttoPZQPossibilityofresistanceduetodrugpressurecannotberuledout39Newdiscoveryofschistosomicidalactivityofartmether(artemisinins)ExtractedfromArtemisiaannuaplants&convertedintosemi-syntheticderivatives.Activeagainstjuvenileformsofallhuman-associatedschistosomespp.tested40EliminationofsnailOncomelania(molluscicide,engineeringmethod)Controlthefecesofdomesticanimals(cattle)andhumansSafewatersupply41Healtheducation42Sudan,Beshirvillage:70%ofpeopleexcreteS.mansonieggs43apondattheendoracanalclosetoavillage44vegetationinthecanalasha