Attitude towards CATT-positive individuals without parasitological confirmation in the African Trypanosomiasis (T.b. gambiense) focus of Quicama (Angola)

Serologically positive individuals without parasitological confirmation con stitute an important problem for trypanosomiasis control programmes because of epidemiological and therapeutical consequences. In July 1997, in the fo cus of Quicama (Angola), 4753 individuals were screened using CATT/T.b.gamb iense on whole blood. In CATT-positive but parasite-negative individuals, C ATT titration on serum was performed. Sixteen individuals showing an end-ti tre lower than 1/4 were considered noninfected according to the results of a previous study of serological status of parasitologically confirmed cases ; 86 individuals with end titres greater than or equal to 1/4 were consider ed suspected of trypanosomiasis and were followed-up from July 1997 to July 1998 with controls every three months. After one year, 32 individuals whos e antibody titres dropped < 1/4 were considered noninfected, 22 were confir med by demonstration of parasites, 17 were further followed-up because anti body titres remained greater than or equal to 1/8 but parasites could not b e found. Fifteen individuals did not show up for testing. Following the usu al criterion, only parasitologically confirmed cases were treated. However, if it had been decided to treat parasite-negative individuals with a CATT end-titre > 1/8, 22 initially unconfirmed but infected individuals would ha ve been treated earlier, whereas 5 noninfected individuals would have been treated unnecessarily. CATT titration on diluted serum or plasma is useful for making therapeutical decisions.