Characterization by isoenzyme electrophoresis of Trypanozoon stocks from sleeping sickness endemic areas of south-east Uganda.

An epidemic of sleeping sickness, which started in 1976 in a focus within the county of Luuka in Central Busoga, has spread to cover the three districts of Busoga and large parts of the neighbouring districts of Tororo and Mukono. Forty-three isolates of the subgenus Trypanozoon from Busoga and Tororo (27 from man, 9 from cows, 2 from pigs and 5 from tsetse flies) were compared by thin-layer starch-gel electrophoresis for seven enzymes. Thirty zymodemes were identified; 17 of them were found circulating in the human population. The zymodemes seen previously in Busoga were still circulating together with several new ones. Of the 16 isolates from cattle, pigs and tsetse flies, only two had the same profile, indicating a high degree of diversity. Two zymodemes from cows and a pig were identical to those found in man, implicating domestic stock in the transmission of human disease in south-east Uganda. A computer analysis of the results produced six main zymodeme groups. One comprised only isolates from man; two were composed of isolates from man, domestic animals and tsetse; and three consisted of stocks from domestic animals only. These groups quite probably indicate the different cycles of transmission involving man, tsetse fly and domestic stock.