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