African horse sickness (AHS) is a highly infectious non-contagious, vector born viral disease affecting all species of Equidae. It is classified as an Orbivirus of the Reoviridae family of which there are 9 serotypes. All serotypes (1-9) are distributed throughout South Africa, although there is a variation in their temporal distribution. It is endemic to (occurs naturally on) the African continent, and is characterised by respiratory and circulatory damage, accompanied by fever and loss of appetite.

AHS does not spread directly from one horse to another, but is transmitted by the Culicoides midge, which becomes infected when feeding on other infected equidae. It occurs mostly in the warm, rainy season when midges are plentiful, and disappears after frost, when the midges die. Most animals become infected in the period associated with sunset and sunrise, when the midges are most active.


Letter ELA to European Commission and Counsil regarding AHS-measures

Emerging Equine Diseases Newmarket conference notes by Anne Lamborn

African Horse Sickness Trust website