The brief overviews presented in chapters 2, 3 and 4 clearly show that tsetse-trypanosomiasis is still a major constraint to livestock agriculture in West Africa, as increased rainfall in recent years has led to favourable habitats for tsetse flies in contrast to the drought conditions of the 1970s and 1980s. Furthermore, the problem of chemoresistance by livestock to the major trypanocidal drugs is spreading in the region. The need to employ a more integrated approach involving various tsetse-trypanosomiasis control methods, including the use of trypanotolerant livestock, has become even more acute now than in the past (FAO, 1998).
The major hindrance to the greater and wider-spread use of trypanotolerant livestock, especially in zero- to low-tsetse challenge areas, was the assumption that they are unproductive in view of their small size. Conclusions and comparisons made in the 1970s and early 1980s between trypanotolerant cattle and susceptible breeds (widely assumed to be more productive) established that this was not the case and that the contrary was in fact true. Further comparisons made in the late 1980s and early 1990s that took into account the milking and traction capacities of trypanotolerant livestock established that even in zero- to low-tsetse challenge areas, the biological productivity of trypanotolerant breeds is highly competitive. The missing information required to promote their wider use was their financial or economic competitiveness (de Haan, 1988). However, such data have been forthcoming in the late 1990s (e.g. Itty et al., 1997; FAO, 2003) and the emerging consensus is that given the number of other important diseases to which trypanotolerant livestock are apparently resistant or tolerant (Mattioli et al., 2000; Claxton and Leperre, 1991), trypanotolerant livestock will continue to play an important role in the development of livestock agriculture in West Africa.
Currently, trypanotolerant livestock are playing significant roles in the control of tsetse-trypanosomiasis in that their use in tsetse-affected areas allows livestock production and related development to occur that would otherwise not be possible with other breeds. The continued use of these animals in the production systems not only assures the livelihood support for the families who keep them but also leads to the conservation of these unique breeds. Their presence reduces the need for tsetse eradication, the results of which may have an as yet unknown impact on land use. Furthermore, some field evidence suggests that the use of trypanotolerant livestock has the potential of reducing trypanosome loads in given locations in view of the low numbers of parasites found in them and their infrequent infection status.
Several factors have been identified as influencing the extent to which trypanotolerant livestock are used or will be used in the future. Among them are changes in ecological settings, production systems, perceptions about their value to producers and availability of results of technologies that have the potential to increase their numbers. In addition, a framework has been constructed that considers these factors by analysing and making decisions about where and under which conditions trypanotolerant livestock would be needed in the future as part of an integrated approach to tsetse-trypanosomiasis control. The expected responses by producers and planners to the use of these breeds and other control methods with changing tsetse-challenge situations, as shown in Table 10, suggest that the trypanotolerance trait will continue to be exploited to support both low-input and market-oriented systems in the future.
In summary, the utility of the decision rules elaborated in Snow and Rawlings (1999) and the predicted responses outlined in Table 10 based on the framework developed in this paper, indicate that planners need to consider a broad range of issues including producers and community leaders views when implementing the control or eradication of tsetse-trypanosomiasis.