Host Susceptibility to African Trypanosomiasis: Trypanotolerance

Abstract

Publisher Summary The exploitation of genetic resistance to disease is an important consideration in livestock development programs, where conventional disease control measures are not effective or are too costly. Such an approach may be directly applicable to African animal trypanosomiasis. In African trypanosomiasis, the control measures currently in use include diagnosis and treatment, chemoprophylaxis, and control or eradication of tsetse with insecticides. At present, there is no effective field vaccine available against African trypanosomiasis. The major constraints to the development of a vaccine include the existence of the different species of trypanosomes and of different serodemes within the same species, all with the capability of producing different repertoires of variable antigen types (VATS). This chapter discusses the available information on the aspects of trypanotolerance, with regard to cattle, sheep, goats, wildlife, and man. It describes experimental results derived from mouse models and the relevance of these models to trypanosomiasis of livestock. The genetic resistance to trypanosomiasis is not necessarily associated with low productivity. Trypanotolerance is not a stable characteristic, and evidence suggests that it can be supplemented or reduced by a number of factors affecting the host and its environment, which include age and sex; maternally-derived immunity, intensity of challenge, virulence, previous exposure, stress, and susceptibility to other diseases. Investigations of trypanotolerance also represent an exciting approach to the important interactions between host and parasite. Trypanotolerance exists as an innate characteristic and that it is probably inherited as a dominant trait. While the level of trypanotolerance can be reduced under certain circumstances, it can also be enhanced, for example, by previous exposure. Therefore, there is hope that it may be possible in the future to supplement the level of trypanotolerance both by genetic selection and by immunological or therapeutic procedures.