Bluetongue is caused by Bluetongue virus, which is transmitted between animals by biting midges (Culicoides). It affects sheep most often, but can infect any of the ruminants. Bluetongue is becoming more of a problem as the vector is adapting to the cooler climates of Europe and is bringing the virus with it. Bluetongue is not a contagious disease but can be spread via surgical equipment and needles. The virus is also found in semen and can be transmitted between animals at the time of mating. Cattle are less commonly affected than sheep but can still be infected by the virus.