Medical Microbiology

596 10 Helminths

mectin(0. 15 mg/kgofbodyweight)administeredonceortwiceayearhas

beenpracticedsince 1987 .Thiscandrasticallyreducethemicrofilarialdensity

inhumanskinforupto 12 months.Microfilariaeintheeyesarealsoin-

fluenced.Thesemeasurespreventdiseaseandreduce,oreveninterruptpara-

sitetransmission.Simultaneousapplicationofvectorcontrolmeasuresand

masstherapywithivermectinhaseliminatedtheparasitereservoirinthe

populations ofsevenofthe 11 Africancountries participatinginthe

above-mentionedcontrolprogram(WHO, 200 0).Themanufacturerofiver-

mectinisprovidingthedrugatnocostfortheWHO-coordinatedprogram.In

furtherdiseasecontrolcampaigns,thevectorcontrolmeasuresaretobe

stopped,butmasstreatmentswithivermectinorotherpotentdrugsare

tobecontinuedonceayearoverthelongerterm(WHO, 200 0).

Dracunculusmedinensis(MedinaorGuineaWorm)

Causativeagentofdracunculosis(MedinaorGuineaworminfection)

MaleDracunculusmedinensiswormsare 1 – 4 cmlong,thefemalesmeasure 50 –

100 cminbodylength.Humanscontractthediseasebyingestingdrinkingwater

contaminatedwithintermediatehosts(“waterfleas”:freshwatercrustacea,Cy-

clops)containinginfectiveDracunculuslarvae.Fromtheintestinetheparasitesmi-

gratethroughthebody,femalesandmalesmateintheconnectivetissue,andafter

approximately 10 – 12 monthsp.i.maturefemaleseventuallymovetothesurfaceof

theskinofthelegsandfeetin 90 %ofthecases.There,thefemaleprovokesan

edema,ablister,andthenanulcer.Skinperforationisaccompaniedbypain,fever,

andnausea;secondarybacterialinfectionsoccurinapprox. 30 %ofcases.Whenthe

woundcontactswater,thefemaleextendstheanteriorendoutofitandreleases

numerouslarvae.Thelarvaeareingestedbyintermediatehostsanddevelopinto

infectivestages.

Diagnosisisusuallybasedontheclinicalmanifestations.

TheWHOhasbeenrunningacontrolprogramsincetheearly 1 980sbasedmainly

oneducationofthepopulationandfiltrationofdrinkingwaterusingsimplecloth

ornylonfilters.Annualinfectionincidenceshavebeenreducedfromthreeanda

halfmillioncasesin 1986 toabout 75000 in 2000 (WHO,2004).Dracunculosisnow

stilloccursin 14 sub-SaharanAfricancountries,buthasbeenofficiallydeclared

eliminatedinsomeformerlyendemiccountries(includingIndia,Pakistan,and

someAfricancountries).Approximately 73 %ofallcasesarecurrentlyreported

fromSudan.

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Kayser, Medical Microbiology © 2005 Thieme