The effect of a topical repellent containing permethrin on the number of Culicoides midges caught near horses with and without insect hypersensitivity in the Netherlands.

Abstract

Insect hypersensitivity in horses is most likely caused by Culicoides spp., although other insects may also play a role. Until now no effective cure has been found for this condition. There are numerous therapeutic and preventive measures used in the control of insect hypersensitivity. One of the preventive methods which can be used to prevent insects biting horses is a topical insecticide. In this study the effect of a topical repellent containing permethrin was examined on horses. Seven pairs of horses were used in this experiment. During two subsequent evenings the Culicoides spp. and other flying insects attracted to the horses were captured. The horses were placed inside a tent trap to collect Culicoides spp. and other insects attracted to the horses. The first evening both horses of the pair were untreated. After the first capture one of the horses was treated with the pour-on repellent. The capture session was repeated the next day. This method seems suitable for testing insecticides on horses. Similar percentages of Culicoides were trapped as in earlier studies in the Netherlands (C. obsoletus 95.3% and C. pulicaris 4.5%). A reduction in numbers of Culicoides spp., percentage of bloodfed Culicoides obsoletus and total number of insects attracted to horses 24 hours after treatment with permethrin, did not reach a statistically significant difference. During the study no negative side effects following the administration of permethrin were found.