Medical Microbiology

612 11 Arthropods

Diagnosisandcontrol.Casehistoryandclinicalmanifestationsprovideim-

portantdiagnostichintsthatrequireetiologicalconfirmationbyidentifica-

tionoftheparasites(Fig. 11 .1b).Apapuleisremovedbytangentialscalpel

excision,whereuponthespecimenismaceratedin 10 %potassiumhydroxide

(KOH),andthenexaminedformitesunderamicroscope.Mitescanalsobe

isolatedfromskintunnelsafterscarificationwithaneedleorbypressing

adhesivetapeontotheskin.Therapyrequirestopicalapplicationofc-hexa-

chlorocyclohexane(lindane),permethrinorcrotamitoninstrictaccordance

withmanufacturer’sinstructions.Arecentdevelopmentisperoraltherapy

withivermectin.Underclothingandbedlinensmustbewashedatamini-

mumtemperatureof 508 C.

OtherMites

ThepreferredhostsofmitesoftheordersAstigmata(e.g.,Sarcoptesscabieivar.suis,

S.scabieivar.canis,Notoedrescati,Psoroptesovis),Prostigmata(e.g.,Cheyletiella,

Neotrombicula),orMesostigmata(e.g.,Dermanyssus,Ornithonyssus)arevertebrate

animals(usuallydomesticanimals),withoccasionalhumaninfestations.Onhuman

hoststhemitesremaintemporarilyonorintheskinwithoutreproducing,causinga

varietyofskinlesionsinvolvingpruritus,mostofwhichabatespontaneouslyif

reinfestationcanbeprevented.Itisimportanttopreventsuchinfestationsbytreat-

ingofmite-infestedanimalsand—ifneeded—bydecontaminatingtheirsurround-

ings.

Somegroupsofnonparasitic(“free-living”)mitesareknowntoinduceallergies.

Theso-calledforageordomesticmites(e.g.,Glyciphagus,Tyrophagus,Tyroglyphus)

developmainlyinvegetablesubstrates(grain,flour,etc.)andcancauserhino-

pathies,bronchialasthma,anddermaleczemas(“baker’sitch,”“grocer‘sitch”)

duetorepeatedskincontactswithorinhalationofdustcontainingmites.Wide-

spreadandfrequentinhumandwellingsareseveralspeciesofhouse-dustmites

(aboveallDermatophagoides pteronyssinus)that areanimportantcause of

“house-dustallergy”(dermatitis,inhalationallergy).

Insects

Lice(Anoplura)

Causativeagentsofpediculosisandphthiriosis(louseinfestations)

&HeadliceandcrabliceoccurmorefrequentlyincentralEuropeandelse-

wherethanisgenerallyassumedandmustthereforealwaysbetakeninto

considerationwhendiagnosingskindiseases. &

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Kayser, Medical Microbiology © 2005 Thieme