Medical Microbiology

Nematoda(Roundworms) 593

mectin)are 99 %effectiveinremovingmicrofilariaefromthebloodforone

yearaftertreatment.Mass-treatmentwithalbendazoleorivermectinisalso

expectedtohaveacontrollingeffectonintestinalnematodes(Ascaris,hook-

worms,Strongyloides,Trichuris).Measurestoavoidmosquitobitesarethe

sameasformalaria.

Loa

Loaloa

Causativeagentofloaosis(loiasis,Loaloafilariosis,Africaneyeworm)

Occurrence,lifecycle,andepidemiology.Thirteenmillionpeoplearein-

fectedwiththisfilarialspeciesinthetropicalrainforestareasofAfrica(wes-

ternandcentralAfrica,partsofSudan)(WHO, 1 995).

Theadultandpre-adultparasites(Table 1 0. 4 )liveinandmigratethrough

thesubcutaneousconnectivetissues.Themicrofilariaeappearinaperiodic

patternduringthedayinperipheralblood(Table 1 0. 4 ,Fig. 1 0. 17 ).Accordingly,

theintermediatehostsarediurnallyactivehorseflyspecies(Tabanidae:Chry-

sopsspecies).Theprepatentperiodisfivetosixmonths.Insomecases,mi-

crofilariaedonotappearinthebloodeveninoldercasesofinfection.The

adultfilariaeliveforseveralyears.

Pathogenesisandclinicalmanifestations.Clinicalsymptomscanoccurtwo

to 12 monthsaftertheinfection.Theyareprobablymainlyallergicinnature.

Thefilariaemigratingthroughtheconnectivetissuescauseedematous

swellingsinthelimbs,face,andbody(“Calabarswellings”)anditchingno-

dules(Fig. 1 0. 16 b).Theinfectionisoftenaccompaniedbybloodeosinophilia.

Migrationofaparasitebeneaththeconjunctivacauseslacrimation,erythe-

ma,andothersymptoms.

Diagnosis,therapy,andprevention.Diagnosisinvolvesobservationoftypi-

calsymptoms,adultparasitesinsubcutisorconjunctivaandmicrofilariaein

peripheralblood(inbloodspecimenssampledduringtheday!)(Table 1 0. 4 ,

Fig. 1 0. 17 ).Thedrugofchoiceisdiethylcarbamazinethatkillsmicrofilariae

anddamagesmacrofilariaeafterlong-termtherapy(N.B.:possiblesideef-

fects).

Mansonellaspecies

SeeTable 1 0. 4 andFig. 1 0. 17 forMansonellaspeciesthatshouldbetakeninto

accountindifferentialdiagnosticprocedures.

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Kayser, Medical Microbiology © 2005 Thieme