Field study and in vitro essay of permethrin-impregnated ear tags (Auriplak) in cattle for control of midges (Culicoides) and bluetongue virus

Auriplak ear tags containing 1,2 g permethrin per tag are registered as a drug of veterinary description in Germany for control of flies and tabanids in cattle during the grazing season. When for the first time in 2006 bluetongue virus occurred in Germany the control of biting midges became needed. However, no information was available about the efficacy of the ear tags with permethrin for repellency and toxicity against the blood feeding vector midges. Therefore field trials with 165 heifers and 20 dairy cows were performed in North Germany in cattle tagged with I and 2 ear tags. Field population of midges were caught by using suction light traps, and by mouth operated aspirators midges were caught directly from the animals bodies. Out of 3.319 midges the occurrence of 9 species of Culicoides were identified and listed according to sexes and engorgement. Alive caught midges of the field population were exposed at 7 d intervals pt to hair clippings, collected from the dorsal and ventral sides of the animals body. Repellency and toxic effect against midges in cattle with 2 ear tags was assessed by direct observation of feeding insects caught directly from the cattle and in the bioassay up till 19 days. Cattle with I ear tag became less protected. Auriplak (permethrin) ear tags for cattle are suggested to be of value to reduce the population of infected midges in cattle herds exposed to BT infection. Furthermore the ear tagging will limit the risk of infection and spread of the BT disease in a certain region where infection in animals has appeared.