Field Evaluation of Deltamethrin and Ivermectin Applications to Cattle onHost-Alighting, Blood-Feeding, and Emergence.

Abstract

The impact of topical applications of deltamethrin and ivermectin to cattle onspp. landing and blood-feeding was studied in this work using sticky traps mounted on Friesian heifers' backs. There was no effect of the insecticides on total numbers oftrapped or the proportion engorged. Deltamethrin and ivermectin treatment did not prevent blood-feeding on these animals. Deltamethrin did result in significantmortality as evidenced by the numbers of dead midges combed from heifers' upper flanks. The proximity of engorged midges on traps to dead midges in the hair suggests that blood-feeding took place despite midges receiving an ultimately lethal dose of deltamethrin. Ivermectin application resulted in a smaller proportion of nulliparous than parous females caught. There was no significant effect of ivermectin on the numbers ofthat emerged from dung samples (butwas small at 0.095 for the Obsoletus group). In cases of suspect animal imports, pour-on or spray applications of deltamethrin could reduce the risk of onward transmission of bluetongue virus.