African horse sickness

African horse sickness virus
Virus classification
Group:	Group III (dsRNA)
Order:	Unassigned
Family:	Reoviridae
Subfamily:	Sedoreovirinae
Genus:	Orbivirus
Species:	African horse sickness virus

African horse sickness (AHS) is a highly infectious and deadly disease. It commonly affects horses, mules, and donkeys. It is caused by a virus of the genus Orbivirus belonging to the family Reoviridae. This disease can be caused by any of the nine serotypes of this virus. AHS is not directly contagious, but is known to be spread by insect vectors.

AHSV was first recorded south of the Sahara Desert in the mid-1600s with the introduction of horses to southern Africa. The virus is considered endemic to the equatorial, eastern, and southern regions of Africa. Several outbreaks have occurred in Equidaes throughout Africa and elsewhere. AHS is known to be endemic in Sub-Saharan Africa, and has spread to Morocco, the Middle East, India, and Pakistan. More recently, outbreaks have been reported in the Iberian Peninsula. AHS has never been reported in the Americas, eastern Asia or Australasia. Epidemiology is dependent on host-vector interaction, where cyclic disease outbreaks coincide with high numbers of competent vectors. The most important vector for AHS in endemic areas is the biting midge Culicoides imicola, which prefers warm, humid conditions. Larvae do not carry the virus and long, cold winters are sufficient to break epidemics in non-endemic areas.

The common hosts of this disease are horses, mules, donkeys, and zebras. However, elephants, camels, and dogs can be infected as well, but often show no signs of the disease. Dogs usually contract the disease by eating infected horse meat, but there has been a recent report of the disease occurring in dogs with no known horse meat ingestion.

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