Enzyme polymorphism and the distribution of<i>Trypanosoma congolense</i>isolates

Conditions were established for demonstrating, by electrophoresis, polymorphism in 12 soluble enzymes from Trypanosoma congolense. Three enzymes had identical mobilities in every stock, variation occurring among the remaining nine. Enzyme profiles were determined in 78 stocks collected from various hosts in a number of African countries, and were used by the computer to establish relationships within the collection. The major groupings formed solely from the isoenzymes corresponded remarkably closely to the origins of the stocks. Two distinct enzymic divisions formed, related only at the 20% level; Division A consisted entirely of stocks isolated in the humid coastal areas of West Africa, while Division B consisted mostly of stocks from drier zones throughout Africa. Some large groupings within these two main divisions also correlated with particular areas of origin within the major ecologic zones. The dry zone Division B included one group almost exclusively from East Africa, and two quite distinct enzymic groups from The Gambia; isolates from Liberia and Ivory Coast tended to fall into separate groups within the humid zone Division A. It is suggested that the differences between the major divisions may be associated with infraspecific adaptation to the different vector species occupying the separate habitats.