Epidemiological studies on the animal reservoir of Gambiense sleeping sickness. Part III. Characterization of trypanozoon stocks by isoenzymes and sensitivity to human serum.

Polymorphism in 12 enzymes, as shown by electrophoresis on thin-layer starch-gel, was examined in 88 stocks of trypanosomes of the subgenus Trypanozoon isolated from man and animals in the Ivory Coast and Upper Volta. Three of the enzyme profiles seen in trypanosomes from man in the Ivory Coast were exactly the same as in trypanosomes from local domestic pigs and from various game animals and a bovine in the Upper volta, thus confirming previous evidence that human trypanosomiasis is a zoonosis in West Africa. Altogether 9 zymodemes were found in man; one was exactly the same as another from the Congo while a further one was identical to a Ugandan zymodeme. Thirty-one zymodemes were found only in animals, and 6 were exactly the same as others from elsewhere in Africa, including the eastern part. All zymodemes resembled each other by possessing common electrophoretic patterns in 5 enzymes. In most zymodemes, the variants of two other enzymes were characteristically West African, although an East African influence was apparent, together with further evidence of hybridization. Many zymodemes differed from others only to a minor extent in a few isoenzyme bands. A group of closely related minor zymodemes constituted another trypanosome population ineffective to man in West Africa which had a variable sensitivity to normal human serum; enzymatically it was clearly separated from the major zymodeme previously described in West Africa, which was consistently resistant to normal human serum and had been previously associated with chronic gambiense sleeping sickness.