Medical Microbiology

Insects 619

whydogandcatfleapopulationscanpersistinhumandwellingsformonths

ifcontrolmeasuresarenottaken.

Epidemiology.Thefleasinthisgroupareperiodicectoparasites.Theadult

stagesremainforthemostpartonthehostwhilethelarvaeandpupae

liveinthevicinityoftheirhostsintheso-called“nesthabitat.”Incertain

regions,fleasserveasvectorsforviruses,bacteria,rickettsiae,protozoa,

andhelminths.Fleasarebest-knownasthevectorsofthecausativeagent

ofplague,Yersiniapestis(rodent-infestingfleasofthegenusXenopsylla,

amongothers).

Clinicalmanifestations.Dermalreactionstofleabitesgothroughseveral

phases:

&Earlyreaction:withinfiveto 30 minutesafterthebite,adotlikehemor-

rhage(atthesiteofthebite)andareddening(erythema)withorwithouta

centralblisterareformed,accompaniedbypruritus.

&Latereaction:after 12 – 24 hours,itchingpapulesform,surroundedbyer-

ythemasuptopalm-size,somewithacentralblisterorpurulentpustule;this

reactionpersistsforonetotwoweeks.

&Predilectionsitesforlesions:extremities,neck,napeofneck,shoulders,

lessoftenthetrunk.Reactionsareusuallyinmultiplegroups,sometimesin

rows.

Diagnosisandcontrol.Adiagnosisisreachedbasedontheskinlesionsand

thecasehistory.Fleasarerarelyfoundonthehumanbody.Itisimportant

tofindthepotentialsourceoffleainfestationonanimalhosts(dog,cat,

hedgehog,birds,etc.)orintheirenvironment,andtoidentifythefleasfound.

Oncethespeciesisknown,specificcontrolmeasurescanbecarriedout.

FleasoftheFamilyTungidae(SandFleas)

Tungapenetrans

Causativeagentoftungaosis(tungiasis)

Morphologyandbiology.Tungapenetrans,thechigoe,jigger,orsandflea,

infesthumansandanimalspecies,forexampledogs.Themales,young

females,andotherstagesliveinsandysoil.Fertilizedfemalesarehighly

activeinquestingforahost.Iftheysucceed,theypenetratetheskinhead

first,thenswellupwithinonetotwoweeks,sometimesreachingthesize

ofapea,fromtheiroriginalsizeof 1 – 2 mminlength.Theylayeggsovera

periodofabouttwoweeks,andthendiewhilestillundertheskin.

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Kayser, Medical Microbiology © 2005 Thieme