Medical Microbiology

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