Sustainability of Tsetse Control by Subsequent Treatment of 10% of a Previously Treated Ugandan Cattle Population with 1% w/v Deltamethrin

This study was conducted in Masaba and Masafu Sub-counties, Busia District, Uganda to assess the effect on the tsetse fly population of first treating all cattle with 1% w/v deltamethrin pour-on for a few months, followed by treating 10% of the cattle population. Treatment of all cattle for 6 months resulted in a significant reduction in the density of tsetse flies from 6.3 to 0.1 flies/trap/day (FTD), a 98.4% reduction. During the same period, the point prevalence of bovine trypanosomosis dropped from 37.7% to 2.9% (a 92.3% reduction). Treatment was resumed six months later, but this time only 10% of the cattle population received the pour-on treatment at three week intervals for a period of one year. This treatment maintained the tsetse fly density between 0 and 0.5 FTD and the prevalence of bovine trypanosomosis generally remained below 10%. In conclusion, under the local prevailing conditions, treatment of all communally grazed cattle with deltamethrin pour-on effectively suppressed the Glossina fuscipes fuscipes population. However, subsequent treatment of 10% of the cattle probably failed to control the tsetse fly population at a level sufficient to reduce trypanosomosis to acceptable levels.