Medical Microbiology

Platyhelmintha(syn.Platyhelminthes) 565

formsoftheinfection.IntheCNS,themetacestodesareusuallylocalizedin

thecerebrum(ventricle,subarachnoidalspace),morerarelyinthespinal

cord;theycancauseepileptiformconvulsions,raisedintracranialpressure,

andotherneurologicalsymptoms.Thecysticercicanalsodevelopinsubcu-

taneoustissues,intheheart,andintheskeletalmusculature.

Diagnosis.Ifmetacestodesarelocalizedinthesubcutis,palpationofsub-

dermalnodulesmaysupplyinitialevidenceofcysticercosis.Toolsuseful

indiagnosinginternalorganinfectionsincludeimagingproceduresandim-

munodiagnosticmethods(Table 11. 5 ,p.625).Inover 90 %ofcasesofcerebral

cysticercosis,theuseofpurifiedglycoproteinantigensfromT.soliummeta-

cestodesinaWesternblotassayrevealsserumantibodies.

Therapy.Praziquantelincombinationwithcorticosteroidshasprovedeffec-

tiveinalargepercentageofcasestreated(includingneurocysticercosis)in

whichthemetacestodeswerenotyetcalcified.Closepatientmonitoringis

requiredforthistherapy.Albendazoleisalsousedintreatmentofhuman

cysticercosis.

Echinococcus

Causativeagentofechinococcosis

&ThemostimportantspeciesofthegenusEchinococcusareEchinococcus

granulosus(intestinalparasiteofCanidae)andE.multilocularis(intestinal

parasiteoffoxspecies,dogs,cats,andothercarnivores).Bothspeciesoccur

inEurope.Theirmetacestodescancausecysticechinococcosis(CE,hydatid

disease)oralveolarechinococcosis(AE)inhumans.Humansareinfected

byperoralingestionofEchinococcuseggs,fromwhichinCE,liquid-filledcys-

ticmetacestodes(thehydatids)develop,particularlyintheliverandlungs.In

AEthemetacestodesprimarilyparasitizetheliver,wherethemetacestodes

proliferatelikeatumorandformconglomeratesofsmallcysts;secondary

metastaticspreadtootherorgansispossible.Clinicalimagingandimmuno-

diagnosticmethodsareusedfordiagnosis.Treatmentinvolvessurgeryand/or

chemotherapy. &

Parasitespecies.Echinococcusspeciesaresmalltapewormsthatparasitize

thesmallintestineofcarnivoresandproduceeggsthatareshedtotheen-

vironmentbythehost.Pathogeniclarvalstages(metacestodes)developfol-

lowingperoralingestionofsucheggsbythenaturalintermediatehosts(var-

iousmammalianspecies),aswellasinhumansandotheraccidentalhosts

(whichdonotplayaroleinthelifecycle).FourEchinococcusspeciesare

currentlyknown,allofthempathogenicforhumans(Echinococcusgranulo-

sus,E.multilocularis,E.vogeli,andE.oligarthrus).

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Kayser, Medical Microbiology © 2005 Thieme