The use of cattle to protect sheep from bluetongue infection.

Studies on the host preferences of Culicoides imicola, the vector of bluetongue virus in South Africa, are reviewed. There is agreement that this species prefers to feed on cattle but will also feed on other bovidae and sheep. Over a seven year period cattle kept near sheep on a Natal farm appear to have appreciably reduced the incidence of bluetongue in the sheep. In addition to immunization this "decoy" approach is therefore recommended to assist in the protection of stock from insect borne diseases such as bluetongue and possibly African horsesickness and Rift Valley fever.