Potential of trypanotolerance as a contribution to sustainable livestock production in tsetse affected Africa

Summary

Tsetse transmitted trypanosomiasis is possibly the major constraint on livestock and agriculture development in Subsaharan Africa. Control of the disease has been based on vector control as well as on the use of trypanocidal drugs to treat or prevent infection in animals. Both control methods are effective but have proven not to be sustainable. Moreover, the development of a vaccine against trypanosomiasis is unlikely to be successful in the near future. On the other hand, trypanotolerant cattle, like the N'Dama can survive and produce in tsetse affected areas without interventions. This taurine breed has been indigenous to Africa for approximately 7,000 years and forms presently about 6% of the bovine population of Africa. Generally the N'Dama are kept in the rural areas by the small‐scale farmer as a multi‐purpose animal. Recent studies have defined management characteristics and assessed the production potential at the village level and under ranching conditions of N'Dama cattle exposed to various levels of tsetse challenge.

Furthermore, experimental infections showed conclusively the superior resistance to the effects of infection of the N'Dama cattle when compared to zebu cattle and have confirmed that trypanotolerance is innate in N'Dama cattle. Studies have been conducted on development of protective humoral and cellular responses, the regulation of parasite multiplication and control of anaemia. These studies provided tools for identifying components of trypanotolerance. The ability to resist the development of anaemia in the face of infection, has shown to be correlated with the capacity to be productive; moreover, PCV values can serve as selection criterium for trypanotolerance. Subsequently, repeatabilities and heritabilities of trypanotolerance and performance traits were estimated. Economically sound selective breeding programmes for increased production and trypanotolerance are now feasible. Finally, studies have been initiated to identify genetic markers to clarify the relationship between genetic variation at the molecular level and variation in trypanotolerance. It is envisaged that in the next decade genetic improvement can be achieved by applying marker assisted selection and introgression of trypanotolerance to other breeds.

Notes

Escudo de Medicina Veterinaria, Universidad Nacional, Apdo 149, 3000 Heredia, Costa Rica.