Medical Microbiology

554 10 Helminths

response(=immunoevasion).Additionalimmunoevasivemechanismshave

alsobeendescribed,e.g.,sheddingpartofthetegumentandsecretionofim-

munosuppressivesubstances.

ThecurrentimmunestatusofpersonsinfectedwithSchistosomaisappar-

entlyalsodeterminedbythebalanceofthoseantibodieswhichenhancethe

above-mentionedimmuneresponse(IgEandperhapsIgA)andothersthat

inhibitit(IgM,IgG2,orIgG 4 ).

Diagnosis.Followingtheprepatentperiod,i.e.,fourto 10 weeksp.i.atthe

earliest,theeggscanbedetectedinstoolspecimensorinurinesediment

(Fig. 1 0. 1 ,p.545,Table 1 0. 2 ,p. 54 7).Theeggscanalsobefoundinintestinal

orurinarybladderwallbiopsies.Immunodiagnosticmethods(Table 11. 5 ,

p.625)areparticularlyusefulfordetectinginfectionsbeforeeggexcretion

begins(importantfortravelersreturningfromtropicalregions!).Detection

ofmicrohematuriawithteststripsisanimportantdiagnostictoolinbladder

schistosomosis.Clinicalexaminationwithportableultrasonicimagingequip-

menthasprovedtobeahighlysensitivemethodofdetectinglesionsinthe

liverandurogenitaltractinepidemiologicalstudies.

Therapy.Thedrugofchoicefortreatmentofschistosomosisispraziquantel,

whichishighlyeffectiveagainstallSchistosomaspeciesandiswelltolerated.

OxamniquineiseffectiveagainstS.mansoni.

Controlandprevention.Currentschistosomosiscontrolstrategiesarebased

mainlyonregulardrugtherapyofspecificpopulationgroups.Morbidity,mor-

tality,andeggexcretionratesareclearlyreducedbysuchprograms.Hygienic

andorganizationalmeasures(constructionoflatrines,improvementofwater

supplyquality,etc.)aimtoreduceSchistosomaeggdisseminationandcontact

withcontaminatedbodiesofwater.IndividualpreventivemeasuresinSchis-

tosoma-contaminatedareasincludeavoidanceofskincontactwithnaturalor

artificialbodiesofwater(freshwater).Drinkingwaterthatcouldbecontami-

natedwithcercariaemustbedecontaminatedbeforeusebyboiling,chlori-

nation,orfiltration.

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Kayser, Medical Microbiology © 2005 Thieme