Estimating the effects of tsetse control on livestock productivity - A case study in southwest Ethiopia

A tsetse control campaign was started in January 1991 using a synthetic pyr ethroid cypermethrin 'pour-on' applied monthly to cattle exposed to high le vels of drug-resistant trypanosomes in the Ghibe valley of southwest Ethiop ia. In December 1992, a cost-recovery scheme was introduced, and thereafter farmers paid for treatment. An average of 100 village Ethiopian Highland Z ebu cattle were monitored monthly from March 1986 to February 1997. Individ ual animals in this herd were treated with diminazene aceturate (Berenil, H oechst, Germany) at 3.5 mg/kg when trypanosomes were detected and their pac ked cell volume was less than 26%. Superimposed on this systematic trypanoc idal chemotherapy, control of tsetse resulted in average reductions from 19 92 to 1996 of 95% and 75% in the mean relative densities of tsetse and biti ng flies, respectively, and of 63% in the prevalence of trypanosomal infect ions in cattle. Despite these reductions, there was no significant increase in the body weight of the cows, calving rate or the mean body weight of ca lves at 12 months of age. There was, however, an average decrease of 57% in calf mortality (including still births) by 12 months of age, an increase o f 49% in the ratio of live calves under 12 months of age to cows over 36 mo nths of age, and an increase of 8% in the body weight of adult males.