There are notable exceptions to practically any general statement about tsetse flies.
An assessment of the nature and rate of development expected in each ecological area, regardless of the presence of tsetse and trypanosomiasis.
Ford, 1971, on the requirements of sound policy
This paper has tried to cover the main methodological issues involved in the economic assessment of area-wide tsetse and trypanosomiasis control programmes. To return to the original theme, the setting up of guidelines for prioritizing projects on the basis of their economic performance, and the analyses and figures above try to illustrate what might be the general trends governing the relative profitability of different approaches towards controlling tsetse and trypanosomiasis. However, as MacLennan (1980, quoted above) and many others have found, generalizing about this disease and its vector can be dangerous, as there is inevitably a good case study to refute any statement. With this caveat in mind, for West Africa, the key questions to be asked are summarized in Box 3. A similar typology was used by Bauer and Snow (PAAT, 1999) to suggest what types of intervention were most appropriate under different tsetse challenge levels.
Given the likely existence in many areas of the two turning points for area-wide long-term control or elimination illustrated in Figure 9, the decision-making process could be something like that shown in Figure 12. This figure must be interpreted in the light of individual situations. In particular, the population densities that define the two unprofitable tails of the benefit distribution (those to the left of turning point 1) and to the right of turning point 2) will vary from area to area, and may fall outside the range of figures given. The GIS priority-setting framework also implicitly filters out these two tails, and it is suggested that the logical point for a more detailed economic analysis to intervene is once the GIS-filtering process has highlighted potential priority areas, as shown in Hendrickx (2001). This still leaves a substantial number of options where such an economic analysis is required, which is why the use of a standardized methodology involving a cost-effective data collection exercise is so important (see Chapter 5). Updating estimates of tsetse control costs, including overheads is obviously one component of this. Once again, what the farmers themselves are currently doing is crucial to the assessment:
in order to assess benefits correctly (what proportion of potential disease losses are already being prevented by farmers actions);
in order to gauge how acceptable the proposed control methods are and whether they would be sufficiently attractive for farmers to invest time and money in contributing to them, in particular to low-cost tsetse control options to be used by them alongside trypanocides;
in order to investigate the implications for poor farmers and livestock keepers of any proposed interventions so as to find out if the interventions are more or less accessible to these groups and will benefit their livestock.
Potential decision tree for the economic analysis of area-wide long-term tsetse control or elimination schemes
These points are also important, since, as has been much debated, the tsetse control techniques available range from the high-tech, top-down techniques that require virtually no input from local farmers, to those that rely on the farmers support and involvement. This in turn affects the existence or absence of large overheads, introduces considerable public and private good issues and has implications for long-term sustainability. These issues are outside the scope of this paper, but it is vital that they be considered at the priority-setting and strategic planning levels.
Finally, from the discussions above, it is possible to characterize the type of situations in West Africa where tsetse control in particular is likely to be economically profitable and those where long-term area-wide projects are not likely to show good returns. These are outlined in Boxes 4 and 5 respectively.
The types of situation described, and their implications for tsetse and trypanosomiasis control have long been known, as has been the need to look at development trends irrespective of the tsetse and trypanosomiasis situation before intervening (Ford, 1971). Hopefully, outlining what might be the priority areas will help to promote sound planning in the context of the area-wide proposals and higher profile currently being given to tsetse control. It is essential, however, that each situation be judged on its own merits, using sound economic methods to investigate how different interventions can improve on what the farmers are already doing, how they can involve farmers and how they fit into the broad sweep of development in that area.