Eco-social analysis of an East African agro-pastoral system: Management of tsetse and bovine trypanosomiasis

Abstract

African animal trypanosomiasis or nagana caused by Trypanosoma spp. and vectored by species of tsetse flies (Glossina spp.). Suppression of trypanosomiasis through trapping of tsetse fly populations was conducted from 1995 to 2005 at and near Luke, Southwest Ethiopia. Odor baited mass trapping technology was used to suppress adult fly populations to very low levels while tryponocidal drugs were used to treat trypanosome infections in cattle. Data on ecological, economic and social variables were collected and analyzed in the context of eco-social dynamics in the community. The bio-economicmodel of Regev et al. [Regev,U., Gutierrez, A.P., Schreiber, S.J., Zilberman, D., 1998. Biological and Economic Foundations of Renewable Resource Exploitation. Ecological Economics 26, 227-242] and Gutierrez and Regev [Gutierrez, A.P., Regev, U., 2005. The bioeconomics of tritrophic systems: applications to invasive species. Ecological Economics 52, 382-396]was used as amethodological framework for qualitative evaluation of the effects of tsetse/trypanosomiasis suppression on ecological, economic and social aspects. An objective function for single farmers was formulated to determine the optimal harvesting level of cattle, exposed to high and low levels of risk from tsetse/trypanosomiasis, as measured by the discount rate (δ) for a given base level pastoral resource (R=pasture or forage for cattle). The socially optimal objective function for resource exploitation by all farmers is that which maximizes the present value of utility of individuals expending revenues (consumption) from the revenue stream in ways that enhance the quality of life and yet assures the persistence of the resource base over an infinite time horizon (i.e., renewable resource sustainability). The bio-economic model predicts that reducing risk (δ) from tsetse and disease increased the cattle populations and their marginal value. The model also predicts that the interaction of decreased δ and increased productivity (θ) can lead to increased human and cattle populations and hence to over-exploitation of base resources (pastures) that lower environmental carrying capacity and reduced sustainability.Trap catches indicated that tsetse populations were reduced to very low levels, while the disease prevalence decreased from 29% to 10%. This led to a substantial increase in cattle