Insecticide-treated cattle for tsetse control: the power and the problems

Trypanosomiasis control increasingly involves financial input from livestoc k owners and their active participation. If control is carried out on small er scales than in the past, methods such as aerial and ground spraying and sterile insect techniques will have reduced application. There will be incr eased reliance on trypanocidal drugs, and bait methods of tsetse control - where flies are attracted to point sources and killed. If drug resistance d evelops, cheap and simple bait methods offer the only means of disease cont rol that might be applied, and paid for, by stockowners themselves. The met hods have been effective in some circumstances, but not in others, and it i s important to understand the reasons for the successes and the failures. A nalysis is presented of the results of two Tanzanian tsetse control campaig ns involving the use of insecticide-treated cattle. Between 1991, and 1996, following the introduction of widespread dipping in the Kagera Region, try panosomiasis declined from > 19 000 cases to < 2400 and deaths from > 1000 to 29. On four ranches in the region, tsetse have been almost eliminated an d trypanosomiasis prophylaxis is no longer used. Similarly aggressive use o f pyrethroids on Mkwaja Ranch in Tanga Region has not had such dramatic eff ects. Tsetse and trypanosomiasis are still common, despite high levels of p rophylaxis and the deployment of approximate to 200 odour-baited targets. T he difference in the results is attributed to a combination of the much sma ller area covered by treated animals at Mkwaja, a greater susceptibility to re-invasion and a more suitable habitat for the flies. A better understand ing of the dynamics of the use of insecticide-treated cattle is needed befo re we can predict confidently the outcome of particular control operations.