Cattle having genetic resistance to disease are being exploited increasingly in livestock development programs, particularly in developing countries where conventional disease control measures are not effective, are too costly to implement, or, as is also common, vaccines are not available. Such an approach is applicable to African trypanosomiasis, a disease of animals carried by the tsetse fly. Certain breeds of cattle are able to survive this disease in tsetse fly endemic areas without the aid of treatment, whereas other breeds rapidly succumb. This survival or resistance trait has been termed trypanotolerance and is generally attributed to the taurine breeds of cattle in West and Central Africa, namely the Ν'Dama and the West African Shorthorn (WAS).