Schistosomesbelongtotheclassofdistomas(trematodes).Theyrankamongthemostfrequentpathogens.Estimationsoriginateinmorethan200million
affectedpeople.Thematureparasitesare6–22mmlong.ThemostimportantspeciesareSchistosomamansoni,S.japonicumandS.haematobium.
SchistosomamansoniiscommoninAfrica,SouthAmericaandMiddleEast.
Schistosomiasis(bilharziosis)is–dependingonspeciesandlocationoftheparasites–adiseaseoftheintestine,liverandspleenresp.urinarypassages.
Humansare(re)infectedbycontactwithfreshwaterwhichiscontaminatedbyovacontainingurineorfaeces.Iflarvaeboreintohumanskin,firstatransient
skinreactionappears(itchwithexanthemaorerythema,byrepeatedlyinfectioncercarialdermatitisispossIBLe).After3-10weeksthemeanwhilesexually
maturewormssynthesizecytotoxicandallergicsubstanceswhichcoursefeverishreactioninhumans(Katayamafever).Theinfectedpersonismostlyharmed
bytheeggs,whichgetintoorgansviabloodexcretingproteinsandglycoproteins.Thepersonreactsunderparticipationofownantibodiesandimmune
complexeswithformationofgranulomaandgranulomatousproliferationinintestineandurinarybladdermucosa.Notexcretedeggsdieafter3weeksandwill
bedissolvedorcalcified.Theaffectedtissuegetsfibrous.Infinalstagebilharziosiswillcausedead.