Medical Microbiology

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TrypanosomabruceigambienseandTrypanosoma
bruceirhodesiense
CausativeagentsofAfricantrypanosomosis(sleepingsickness)

Parasitespeciesandoccurrence.Thecausativeagentsofsleepingsickness
areconsideredtobeasubspeciesofTrypanosomabruceiandthereforetheir
taxonomicallycorrectdesignationsareTrypanosomabruceigambienseand
Trypanosomabruceirhodesiense.Inthefollowingtexttheywillbedesignated
asT.gambienseandT.rhodesiense.Morphologically,thesetwosubspecies
differneitherfromoneanothernorfromTrypanosomabruceibrucei,one
ofthecausativeagentsofthenaganaindomesticanimalsthatdoesnotinfect
humans.Thesesubspeciescanbedifferentiatedbymeansofbiologicalcri-
teria(e.g.,hostspecificity,sensitivitytohumanserum)aswellasisoenzy-
maticandDNAanalysis.
Sleepingsicknessoccursonlyinsub-SaharanAfricainregionsbetween
14 northand 20 southlatitudewherethevectors(tsetseflies)areendemic
(Fig.9. 4 ).Currentlybetween 300000 and 500000 personsareinfectedin
theheterogeneouslydistributedendemicareasin 36 Africancountries.
Theofficialnumbersofnewcasesdiagnosedannually(1999: 4500 0)are
unrealisticallylowbecauseofthelarge numbersofunregistered cases
(WHO, 200 0).Insomeareas,sleepingsicknesshasoccurredinincreased,

Trypanosoma 485

DistributionofSleepingSicknessinAfrica

Zaire

Nigeria Sudan

Angola

Fig.9. 4 WestofthedottedlinepreponderanceofTrypanosomagambiense,east
ofthelineT.rhodesiense(accordingtoWHOTech.Ser. 881 ,Geneva:WorldHealth
Organization; 1 998).

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Kayser, Medical Microbiology © 2005 Thieme

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