Butox® 7.5 pour on: a deltamethrin treatment of sheep and cattle: pilot study of killing effects on Culicoides species (Ceratopogonidae)

Topical treatment (at the neck and along the vertebral column) with deltamethrin (Butox® 7.5 pour on) of cattle (30 ml/400-kg body weight) and sheep (10 ml/60-kg body weight) was done to find out, whether the insecticide may reach in a sufficient dosage the legs, which are known to be the main biting site of Culicoides specimens that are the vectors of the recently introduced Bluetongue virus in central Europe. At days 7, 14, 21, 28, and 35 after treatment, some hair was cut off from the legs—close to the claws. Freshly (the night before) caught Culicoides obsoletus specimens were then exposed for 15, 30, 60, or 120 s to such hair and afterwards transferred to a filter paper within plastic Petri dishes to observe their fate. It turned out that even a short contact of 15 s of the Culicoides specimens with deltamethrin-treated hair of cattle or sheep was sufficient to paralyze and kill Culicoides specimens within a reasonable short time even when the hair were cut off at day 28 after treatment. While the results obtained in cattle and sheep were rather similar for days 7 and 14 after treatment, the speed of the killing effect of treated hair of cattle on Culicoides considerably slowed down beginning from day 21 after treatment. However, all the experiments clearly showed that the insecticide deltamethrin may reach the feet of cattle and may kill Culicoides specimens when the product is poured along the vertebral column. Such a treatment may considerably reduce the risk of transmission of the agents of disease. However, in the case of the thick fleece of sheep, the insecticide must be poured directly into the skin to reach full activity.