Medical Microbiology

EntamoebahistolyticaandOtherIntestinalAmebas 499

insmearsorexcisedspecimensfromtheedgesoftheskinlesions.Morere-

liably,theparasitescanbedetectedbycultivationorPCR.Serologicalanti-

bodytestsarepositiveinonlyasmallproportionofcases.

Therapyandprevention.TreatmentofVLisusuallydonewithpentavalent

antimonials(meglumineantimonate,sodiumstibogluconate)pentamidine,

oramphotericinB.Therecurrencerateisrelativelyhigh,especiallyinHIV

patients.Miltefosine,anewlydevelopedandwelltoleratedantitumoralkyl-

phospholipidfororalapplication,hasprovedeffectiveagainstVL.Various

formsofCL(forinstanceL.majorandL.tropica)canbeinfluencedbyinjecting

antimonial preparationsintothelesions;mucocutaneousleishmaniosis

(L.braziliensis)istreatedsystemicallywithantimonials(seeabove,ampho-

tericinB,orpentamidine).Aneffectivechemoprophylaxishasnotyetbeen

developed.ItisthereforeimportanttopreventPhlebotomebiteswithfine-

meshed,insecticide-impregnated“mosquitonets”(p.535).Controlofthe

vectorsinvolvesuseofinsecticidesandeliminationofbreedingplaces.

EntamoebahistolyticaandOtherIntestinal

Amebas

Causativeagentsofamebosis(entamebosis,amebiasis)

&Ofthevariousamebicspeciesthatparasitizethehumanintestinaltract,

Entamoebahistolyticaissignificantasthecausativeagentoftheworldwide

occurringentamebosis,adiseaseparticularlyprevalentinwarmercountries.

Thevegetativestages(trophozoites)ofE.histolyticaliveinthelargeintestine

andformencystedstages(cysts)thatareexcretedwithfeces.Theinfectionis

transmittedbycystsfromonehumantoanother.ThetrophozoitesofE.his-

tolyticacanpenetrateintotheintestinalwallandinvadetheliverandother

organshematogenouslytoproduceclinicalformsofamebosis,mostfre-

quentlyintestinalameboses (amebicdysentery) andhepaticamebosis

(“amebicliverabscess”).Diagnosisofanintestinalinfectionisprimarilycon-

firmedbydetectionoftheparasitesinstool.Ifaninvasive,intestinalorex-

traintestinalinfectionwithE.histolyticaissuspected,aserologicalantibody

testcanalsoprovidevaluableinformation.Morphologically,E.histolyticais

indistinguishablefromtheapathogenicEntamoebadispar(collectivetermfor

bothspecies:E.histolytica/E.disparcomplex). &

Occurrence.InendemicareasinAfrica,Asia,andCentralandSouthAmerica

upto 7 0–90%ofthepopulationcanbearecarriersofE.histolytica/E.dispar, in

theUSAandEuropeabout 1 – 4 %.Worldwidetheannualnumberofnewcases

isestimatedat 48 million,withabout 70000 lethaloutcomes(WHO, 199 8).

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Kayser, Medical Microbiology © 2005 Thieme