Medical Microbiology

610 11 Arthropods

stagesofticksinhabitgrass,ferns,andbranchesinthislowvegetationeither

quiteclosetotheground(mainlylarvaeandnymphs)orsomewhathigher

(uptoabout 80 – 100 cm,mainlyadults)inquestingforsuitablehosts.When

hostsapproach,thetickseitherletthemselvesdropontothemorclingtothe

skinoncontact.I.ricinusbecomesactiveat 7 – 108 C.Maximumtickactivityis

registeredintheperiodsMay-JuneandAugust-October.

ThegreatepidemiologicalsignificanceofI.ricinusincentralEuropeispre-

dominantlyduetoitsfunctionasvectorofthecausativeagentsofLymebor-

reliosis(Borreliaspp.,p. 32 4f.)andtheEuropeantickborneencephalitis(TBE)

(virusofTBE,p. 4 43f.).InnorthernandeasternEuropetheTBEvirusistrans-

mittedbyIxodespersulcatus;Ixodesscapularis(syn.I.dammini)isthevector

ofBorreliaburgdorferiintheUSA.

Diagnosis.IdentificationofI.ricinusiseitherdonemacroscopicallyorwith

thehelpofamagnifyingglass.Differentialspeciesidentificationrequiresthe

skillsofaspecialist.Skinreactions,inparticulartheerythemachronicummi-

gransresultingfromaborreliosisinfection,oftenprovideindirectevidenceof

anearliertickbite.

Tickbiteprevention.Tickhabitatswithdenseundergrowth,ferns,andhigh

grassesshouldbeavoidedasfaraspossible.Ifthisisunavoidable,propercloth-

ingmustbeworn:shoes,longsocks,longtrousers(tucklegsoftrousersinto

socks),longsleevesthatfitcloselyaroundthewrists.Additionalprotectionis

providedbysprayingtheclotheswithacaricides,especiallypyrethroids,which

haveacertainrepellenteffect(e.g.,flumethrin).Theeffectofrepellentsapplied

totheskin(seemalaria)isinmostcasesinsufficienttoprotectagainstticks.

Afterstayinginatickhabitatpersonsshouldsearchtheirentirebody

forticksandremoveanyfoundattachedtotheskinasquicklyaspossible

bymechanicalmeans(donotapplyoilorothersubstancestoattachedticks!).

Anybitesshouldbewatchedduringthefollowingfourweeksforsigns

ofreddening(erythema),swelling,andinflammation.A“migrating,”i.e.,

spreadingrash(erythemamigrans)isindicativeforaBorreliainfection.

Ontheotherhand,thissignisnotobservedinallinfectedpersons.

Mites

Sarcoptesscabiei

Causativeagentofscabies(“theitch,”“sarcopticitch”)

&InfestationwithSarcoptesscabieivar.hominiscauseshumanscabies,a

conditioncharacterizedbypronouncedpruritus,epidermalmiteburrows,

nodules,andpustules.Transmissionispersontoperson.Variousmitespecies

thatparasitizeanimalsmayalsoinfestthehumanskinwithoutreproducing,

causingthesymptomsof“pseudoscabies.” &

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Kayser, Medical Microbiology © 2005 Thieme