Investigation of the efficacy of flumethrin pour-on for the control of high tsetse and trypanosomiasis challenge in Kenya.

The effects of bi-weekly flumethrin pour-on treatments at 1 mg kg bodyweight on tsetse fly population and trypanosome infection rates were monitored over a one-year period (2/89-2/90) in 2000 head of cattle on a trial farm, located in the Lamu District in East Kenya, an adjacent control farm and a transsecting road for additional fly monitoring. The tsetse fly population on the trial farm dropped from pretreatment counts of 118 flies/trap/week (Feb. 1989) to 13 in June 1989 and 32 in Jan. 1990. During the same period and months the fly population in the control farm was 90.34 and 87 flies/trap/week. Fly counts on the transsecting road, however, increased from 72.53 to 163 flies/trap/week. The impact of tsetse fly control is clearly reflected in the reduction of trypanosome infection rates on the trial farm, e.g. 37% (pre-treatment infection rate), 10% and 11% in January, June and December 1989 respectively. On the control farm the infection rates remained at distinctly higher levels of 34%, 17% and 24% during the same period. Mean weekly weight gains were 66% higher in the treated herd as compared to the untreated control herd.