Medical Microbiology

618 11 Arthropods

Fleas(Siphonatera)

Causativeagentsoffleainfestation

&The“humanflea”(Pulexirritans)israre,buthumansarefrequently

attackedbyfleaspeciesthatnormallyparasitizeanimalspecies.Bitereac-

tionscanbeidentifiedonthehumanskin,buttheparasitesmustbefound

andcontrolledonanimalsorintheirenvironment.Travelerstotropicalareas

maybecomeinfestedwithsandfleas(Tungapenetrans). &

Speciesandoccurrence.Atleast 2500 speciesoffleashavebeendescribed

worldwide.About 100 oftheseoccurincentralEurope,ofwhichthemedi-

callyimportantspeciesbelongmainlytothefamiliesPulicidaeandCerato-

phyllidae.EncounterswithPulexirritans,theso-called“humanflea,”arerare,

buthumansareoftenbittenbyfleaspeciesnormallyfoundonanimals,e.g.,

thedogflea(Ctenocephalidescanis),catflea(Ctenocephalidesfelisfelis),

hedgehogflea(Archaeopsyllaerinacei),andEuropeanchickenflea(Cerato-

phyllusgallinae).Allfleaspeciesshowlowlevelsofhostspecificityandthere-

foremayinfestvariousanimalspeciesaswellashumans.

Duetotheirlifecyclethesandfleas(familyTungidae)representaspecial

groupofthefleas.Tungapenetrans,endemicintropicalAfricaaswellasCen-

tralandSouthAmerica,isthemostimportantspeciesinthisfamilyfroma

medicalpointofview.Sandfleainfestationisoccasionallyreportedintrave-

lersreturningfromtropicalregions.

FleasoftheFamiliesPulicidaeandCeratophyllidae

Morphology.Thefleasinthisgroupareabout 2 – 5 mmlong,laterallyflat-

tened,winglessandhavethreepairsoflegs,thehindmostofwhicharehighly

adaptedforjumping.Themouthpartsformabeaklikeproboscisforblood-

sucking,theantennaeareshort.Combsofspines(ctenidia)canadornthe

headandfirstthoracicsegment(Fig. 11 .1f).

Lifecycle.Fleasareectoparasitesinhumansandvertebrateanimalspecies.

Frequentbloodmealsareneededduringtheonetothreemonthegg-laying

period.Mostoftheeggsfalloffthehostandcontinuetodevelopincracksand

crevices(e.g.,betweenfloorboards,underrugs,underdogorcatcushionsor

inbirds’nests).Thelifecyclefromeggtoadultincludesthreelarvalstagesand

onepupalstageandtakesthreetofourweeksunderidealconditions.This

timeperiodcanalsobeextendedbyamatterofweeksdependingonthe

environmentalconditions.Thelifespanofanadultfleavariesfromafew

weekstooneyearincludinglongerstarvingperiodsaswellaseggand

pupasurvivalmaximaofeightandfivemonths,respectively.Thisexplains

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Kayser, Medical Microbiology © 2005 Thieme