Population genetics of Trypanosoma brucei in central Africa: taxonomic and epidemiological significance.

In order to estimate the value of population genetics for both the taxonomy of trypanosomes belonging to the species Trypanosoma brucei and a better understanding of Human African Trypanosomiasis (HAT), we undertook a cellulose acetate electrophoresis isoenzyme study involving 55 stocks isolated from man and animals in Congo, Zaire and Cameroun. Out of the 24 loci surveyed, 15 exhibited variability, which made it possible to delimit 23 zymodemes, divided into 2 groups. The first group equated to the classical subspecies Trypanosoma brucei gambiense, while the second corresponded to the classical subspecies Trypanosoma brucei brucei. These results broadly agree with the current taxonomy, and are corroborated by RFLP analysis of kDNA. Statistical analysis indicates a basically clonal reproduction system of the trypanosomes in the area studied; the zymodemes are equivalent to natural clones (or a family of closely related clones), stable in space and time. Epidemiological hypotheses are proposed according to the geographic distribution of the clones in this area.