Medical Microbiology

Pathogenesisandimmunology.Thecourseoftheinfectionischaracterized

bysuccessivewavesofparasitemiacausedbyantigenicvariationinsucces-

sivetrypanosomepopulations(seeabove).Paralleltoanincreasingparasite-

mia,IgMantibodiesareproducedthataredirectedagainstacertainvariant

specificsurfaceantigen(VSSA)ofthetrypanosomes,whereupontheyelim-

inatethesegmentoftheparasitepopulationbearingthisVSSA.Theparasi-

temiathendeclines,butthetrypanosomeswithadifferentVSSAmultiply,

whereuponspecificantibodiesareonceagainproduced.Antigenvariation

isoneofanumberofstrategiestocircumventhostdefenses(immunoeva-

sion).AboutthetimewhenoneVSSAvariantoftrypanosomesisbeingelimi-

natedfromthebody,theconcentrationsofIgGantibodiesriseandimmune

complexesform.

Trypanosoma 489

Table9. 3 InfectionCourseandClinicalManifestationsofSleepingSickness

Stage,courseand

symptoms

T.gambiense T.rhodesiense

1 ststage:Febrile-glandularorhemolymphaticphase

&Trypanosomechancre InAfricans:<5%

InEuropeans:

approximately 20 %

Approximately 50 %

&Onsetofparasitemia: 2 – 3 weeksp.i. 1 – 2 weeksp.i.

&Typeofparasitemia: Low-level,intermittent High-level,oftenpersistent

&Parasitemia-associated

symptoms:

Fever,chills,headache,jointandmusclepain,transi-

toryedemas,weightloss,generalizedlymphadenopa-

thy(swellingoflymphnodesinneck=Winterbot-

tom’ssign);cardiacdysfunction(especiallyinT.rho-

desienseinfections),anemia,thrombocytopenia,

raisedserumIgM

Course: Chronic(alsoacuteinpersonswithoutimmunity)

2 ndstage:Meningoencephaliticphase

&Penetrationoftrypano-

somesintoCNS:

4 – 6 monthsp.i.orlater Frequentlyafteronlyafew

weeks

&Symptoms: Signsofprogressivemeningoencephalitis,epilepti-

formconvulsions,latersomnolence,apathy,coma.

Pleocytosisincerebrospinalfluid,raisedtotalprotein

andIgMlevels.

Durationofdisease,

bothstages

Monthsto> 6 years Rarely> 3 – 7 months

9

Kayser, Medical Microbiology © 2005 Thieme