anddomesticmammals.Themostimportantinepidemiologicaltermsare
dogs,cats,rodents,chickens,opossums,andarmadillos.Asidefromthere-
duviidvector,T.cruzicanbetransmittedbetweenhumansbybloodtransfu-
sions,diaplacentalinfection,ororgantransplants.
Clinicalmanifestationsandpathogenesis.Someinfectedpersonsreactto
entryoftheparasiteintotheskinorconjunctivawithalocal,inflammatory
dermalreaction(chagoma)orconjunctivitiswitheyelidedema(Roman ̃a
sign).Thefollowingsymptomsareobservedintheacutephase,whichfol-
lowsanincubationperiodofsevento 30 days:fever,edema,lymphnode
swelling,hepatomegaly,splenomegaly,myocarditis,and,lessfrequently,me-
ningoencephalitis.Beginningabouteightto 10 weeksaftertheacutephase
theinfectionturnstoaninapparentphase:serumantibodiesaredetectable,
asareparasitesin 20 – 60 %ofcases(bymeansofxenodiagnosis).Clinicalman-
ifestationsofthechronicphase,oftenstarting 10 – 20 yearsaftertheacute
phase,arecardiopathy(cardiomegaly, 30 %ofcases),digestivetractdamage
(megaesophagus,megacolon,etc., 6 %),andneuropathies(3%).
Theimportantpathogenicprocessesincludeimmunologicallyinduced
destructionofganglialcellsintheautonomicnervoussystemthathavead-
sorbedT.cruziantigen(resultingindysfunctionandorganomegalyinvarious
organs)andinflammatoryprocesses,especiallyinthemyocardialtissues,
probablytheresultofautoimmunereactions.InapparentT.cruziinfections
canbereactivatedbyAIDS.
Diagnosis.Intheacutephase,trypanosomesaredetectableinperipheral
bloodattheearliestonetotwoweeksafterinfection(thickbloodfilms,cen-
trifugationinhematocrittubes,bloodcultures;sensitivity 60 – 100 %).Inthe
chronicphase,detectionoftheparasitesbyconventionalmeansisnolonger
reliable(sensitivity< 10 %).Toolsfordetectionoflow-levelparasitemiasin-
cludexenodiagnosis(fromxenos,foreign:reduviidsfreeoftrypanosomesare
allowedtosuckthebloodofpersonsinwhomaninfectionissuspectedor
suckpatientbloodthroughamembrane;afterafewweeks,thereduviids
areexaminedfortrypanosomes)orspecificDNAdetectionbyPCR.The
apathogenicspeciesTrypanosomarangelimustbetakenintoconsideration
indifferentialdiagnosis.Serologicalmethodsarealsoavailablethatcanbe
diagnosticallyusefulinthechronicphaseinparticular(Table 11. 5 ,p.625).
Therapyandprevention.Intheearlyphaseofaninfection,cureratesof 80 %
havebeenachievedwithnifurtimoxandbenznidazole.Bothofthesepre-
parationsfrequentlycausesideeffects.Preventivemeasuresconcentrate
mainlyonvectoreradicationwithinsecticides,improvementoflivingcondi-
tions,individualprotectionfromreduviidbiteswithmosquitonets(see
Malaria,p.535),andmeasurestopreventtransfusionandtransplantation
infections.492 9 Protozoa9
Kayser, Medical Microbiology © 2005 Thieme