Trypanosomosis agglutination card test for Trypanosoma brucei rhodesiense sleeping sickness.

Objective: To develop a simple field test for diagnosis of Trypanosoma brucei rhodesiense in man. Design: Trypanosomosis Agglutination Card Test (TACT) was developed for the diagnosis of sleeping sickness due to Trypanosoma brucei rhodesiense infection, based on stabilised procyclic forms derived from Utat 4.1. Procyclics were fixed in buffered formalin at 4° for 24 hours and further stabilised in acid/alcohol mixture for 30 minutes. The fixed antigen was stained with Coomassie blue and suspended in 0.1M PBS/sodium azide buffer pH 7.2 at a concentration of 1 x 10 8 trypanosomes/ml and kept at room temperature. This antigen was used to screen 100 sera from rabbits infected with T. b. rhodesiense, eight from normal rabbits, and 220 only sera 60 of which were from sleeping sickness patients, 50 from normal persons and 110 from other parasitic infections. Setting: Laboratory testing of the antigen types against the rabbit and human sera infected with cloned variable antigen types of T.b. rhodesiense, was routinely carried on test cards under room temperature. Subjects/participants: Serum samples from normal and infected rabbits and human subjects. Results: All sera from infected rabbits and 59 from sleeping sickness patients reacted strongly with the antigen showing agglutination reaction which ranged from 1:4 to 1:1024 serum dilution. There was minimal cross reaction with other parasitic infections as follows: one out of 20 malaria patients none of the 20 hookworm patients, one out of 30 for schistosomiasis patients, none of the 10 amoebiasis patients and one out of 20 for filariasis patients. Agglutination titres from all these non-sleeping sickness patients were below 1:16. Based on rabbit positive and negative sera, TACT gave a sensitivity and specificity of 100% and 80% while for human sera a sensitivity of 98.3 % and specificity of 96% were observed. Conclusion: These preliminary results show that TACT could be a promising screening field test for T.b. rhodesiense sleeping sickness.