Chemical control of Haematobia irritans with 0.5% topical ivermectin solution in cattle

A field trial was conducted to evaluate the efficacy of a topical formulati on of ivermectin administered at the dose of 500 mu g/kg against horn flies (Haematobia irritans) in cattle. Eighty-eight cattle in four herds natural ly exposed to horn flies were used in the trial. Replicates were formed of two herds. Within replicates, one herd was randomly allocated to the untrea ted control and the other to the ivermectin treatment group. Horn fly count s were taken on the treatment day (Day 0) and on Days 7, 14, 21, 28, and 35 post-treatment. There were no horn flies on any cattle in the treatment gr oup, whereas all the control cattle were continuously infested by horn flie s on each examination day.