Medical Microbiology

infull-blownAIDSstage),forexample,withmultiplecoagulativenecroses,

small-focushemorrhages,andsurroundingedema.Otherorgansystems

areaffectedmorerarely(inabout 15 %ofcases),e.g.,myocardiumandlungs.

PrenatalToxoplasmosis

Occurrence.Theprenatalfetalinfectionoccursonlyinmotherswhocontract

theirprimary(first!)infectionwithtoxoplasmasduringpregnancy!Thereis

noriskofprenatalfetalinfectioninwomenhavingalatentinfectionwith

serumantibodiesatconception.

Incidence.Therateofverifiedprimaryinfectionsinpregnantwomenwas

estimatedinGermany,Austria,andSwitzerlandin 1995 at0.5–0.7%.Apre-

natalfetalinfectionistobeexpectedinsomeofthesecases,wherebythe

infectionriskforthefetusislowerinthefirsttrimesterthanlaterinthepreg-

nancy.Thefrequencyoftoxoplasmosisinnewborns(prenataltoxoplasmosis)

isbetween0. 1 and0.3%invariousEuropeancountries.Therateislowerin

somecountries,e.g.,inAustria(0.0 1 %),wheremonitoringexaminationsfor

pregnantwomenhavebeenobligatoryforanumberofyears(fordetailssee

Aspo ̈ck, 200 0,p. 6 60).

Possibleconsequencesofprenatalinfection:

& 10 %clinicallyseverecases, 85 %ofthesewithbraindamage(e.g.,hydro-

cephalus,intracerebralcalcifications), 15 %perinataldeaths,

& 15 %mildersymptoms(99%chorioretinitis, 1 %braindamage),

& 75 %subclinicalcases(1 5 %nodamage, 85 %chorioretinitis).

Childreninthislastgroupappeartobeclinicallynormalatbirth,butsignsof

brainandeyedamage,aswellasothersymptoms,maymanifestlaterinin-

fancyandearlychildhood.

Diagnosis.Inimmunocompetentadults,toxoplasmosisisnormallydiag-

nosedserologicallybydetectionofparasite-specificIgGandIgMantibodies

(Table 11. 5 ,p.625).IgMantibodiescanbedetectedasearlyasoneweekafter

theprimaryinfection,peakwithintwotofourweeks,thendroptobelowthe

detectionlimitwithinafewweeks;insomecasespersistenceatlowtiters

lastslonger.IgGantibodiesappearsomewhatlater,peakaftertwotofour

monthsandpersistformanyyears.AhighorrisingIgGtiterwithcontemporal

detectionofIgMindicatesanacuteprimaryinfection.Theisolatedcasesof

oculartoxoplasmosisnormallycannotbediagnosedbyserologicalmethods.

Serologicalfindingsareoftennotreliableindicatorsinimmunodeficient

patientsduetoreducedantibodyproduction.Thecerebralformoftheinfec-

tionseenfrequentlyinreactivatedtoxoplasmosisisthereforeusuallydiag-

nosedbymeansofclinicalimagingmethods.

Toxoplasmagondii 513

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Kayser, Medical Microbiology © 2005 Thieme