EPIDEMIOLOGIC EVIDENCE FOR IMMUNITY FOLLOWING TRYPANOSOMA-BRUCEI-GAMBIENSE SLEEPING SICKNESS

In order to investigate whether protective immunity appears after Tryp anosoma brucei gambiense sleeping sickness, we undertook a retrospecti ve cohort study of 3 remote villages in central Zaire (total populatio n 1431), in which 38% of all adults had a past history of human Africa n trypanosomiasis. Among adults previously diagnosed with trypanosomia sis and treated, the risk of a second episode of trypanosomiasis durin g the 10 years period of observation was only 15% (with a 24 months re fractory period) and 30% (without a refractory period) of the risk of a first episode in adults never previously diagnosed. We could not dem onstrate a similar difference among children, to some extent because o nly a few of them were diagnosed for a first time with trypanosomiasis . Our findings suggest that very significant immunity appears after Ga mbian sleeping sickness, and that developing a vaccine against this su bspecies of trypanosomes is biologically plausible.