Identification of T. brucei-subgroup strains isolated from game

Several T. brucei-subgroup strains isolated from game were investigated with the blood incubation infectivity test (BIIT) and in human volunteers. Original isolates and their clones derivatives were tested. In order to check the validity of the BIIT, volunteer tested clones were used under modified BIIT conditions. Inoculation of different trypanosome strains into volunteers yielded positive parasitaemia for original isolates from lion, hyaena, and Coke's hartebeest. Changing antibody titers during the course of infection in the volunteers were checked with the indirect fluorescent antibody test (IFT). The BIIT WAs reliable (consistently positive) for cloned T. b. rhodesiense. When testing T. b. brucei, the BIIT results depended on the number of incubated parasites and on the parasitaemia peak number the tested trypanosomes derived from. It was further shown that the in vivo part of the BIIT is actually essential for the complete neutralization of T. b. brucei induced by the action of human plasma. Tests with trypanosomes originating from experimentally mixed T. b. rhodesiense and brucei infections gave inconsistent results. On the other hand, pure populations mixed in vitro-prior to incubation for BIIT-revealed results depending on the proportion of the 2 species: up to 20% T. b. rhodesiense gave negative, higher concentrations consistently positive results.