The effect of human serum in vitro on Trypanosoma (Trypanozoon) brucei species trypanosomes and its relationship to infectivity in the blood incubation infectivity test.

All attempts to identify Trypanosoma (Trypanozoon) brucei species trypanosome strains by their sensitivity or resistance to human serum in vitro have so far been unsuccessful. Wet-film examination of T.(T.) b. brucei, T. (T.)b. rhodesiense and T. (Nannomonas) congolense trypanosome strains, both before and after in vitro incubation in fresh human blood for 5 hours at 37 degrees C showed that serum-sensitivity or serum-resistance is not a constant and reproducible property of a trypanosome strain and is totally unrelated to infectivity.