Midges (Culicoides spp.) are vectors of Bluetongue virus (BTV) as well as other viral diseases of livestock. Treating ruminants with pyrethroids could reduce the infection risk by a repellent or lethal effect for midges resulting in a reduced contact between vector and host. In this study, the efficacy of a Deltamethrin formulation against midges attacking sheep is investigated in field studies performed on a farm in Groß Kreutz, Brandenburg.