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Features of Epidemiological Importance in the Development of Cyclically Transmitted Stocks of Trypanosoma Congolense in Vertebrate Hosts

The epidemiological importance of differences in transmissibility, infectivity, antigenicity, pathogenicity and drug sensitivity among species and strains of the African pathogenic trypanosomes is well known. These aspects of trypanosomiasis have been studied particularly intensively in the case of Trypanosoma brucei, but less attention has been given to T. congolense and T. vivax, the two most serious trypanosomal pathogens of domestic livestock. Our recent studies have included experiments involving the cyclical transmission by Glossina morsitans of stocks of T. congolense from locations in East and West Africa to rabbits, calves and sheep, and examinations of formation of local skin reactions and the antigenicity of the trypanosomes developing in these hosts. Differences have been observed in the occurrence of local skin reactions in different host species, and antigenic differences have been found between trypanosome stocks from different areas by serological tests and immunisation and challenge experiments. Differences in the serological responses of rabbits to different trypanosome stocks have also been observed during estimations of antibody levels using enzyme-linked immunosorbent assays.