African horse sickness (AHS) is a noncontagious viral disease affecting all species of equidae. It is caused by one or more of the nine different serotypes of an orbivirus of the family Reoviridae. The disease is characterised by alterations in respiratory and circulatory functions. While the disease is usually fatal in horses, other equine species and their crossbreds may display only mild clinical signs.
Transmission: because AHS is transmitted by at least two species of Culicoides midges, its occurrence is also affected by the seasonal changes in climatic and environmental conditions of the vector's habitat.
Occurrence: all serotypes of AHS virus occur in eastern and southern Africa; this distribution reflects that of zebra, but also of the African donkey, which cycle the virus asymptomatically. In West Africa AHS serotype 9, 7 and 2 are found. Examples of the occasional outbreaks that have occurred outside sub-Saharan Africa are the pandemic in certain countries of the Middle East up to India and Turkey (1959-1961), the outbreaks in Spain (serotype 9, 1966) and the epidemic caused by serotype 4 in Spain (1987-1990), Portugal (1989) and Morocco (1989).
Laboratory diagnosis of AHS, based on the identification of infectious virus, virus nucleic acid, viral antigens or specific antibodies, is of great importance, as the characteristic clinical signs and lesions can be confused with those of other diseases.
It is a listed disease according to the World Organisation for Animal Health (OIE). This means it is a transmissible disease that has the potential for very serious and rapid spread, irrespective of national borders, that is of serious socio-economic or public health consequence and that is of major importance in the international trade of animals and animal products.
During its 80th General Session, the World Assembly of Delegates of the OIE adopted Resolution No. 19 adding African horse sickness (AHS) to the list of diseases for which status is officially recognised by the OIE in accordance to the relevant provisions of the Terrestrial Code. According to Resolution No. 19 adopted during the 82nd General Session in May 2014, all 28 Member States are includes in the list of African Horse Sickness free Member Countries of OIE.
For more details, click on the OIE technical card on African horse sickness.
Community rules for the control of African horse sickness are laid down in Council Directive 92/35/EEC . The measures include, in addition to vector controls, stamping out of infected animals, movement restriction and possibly vaccination within an area of 100 km around the infected premises (protection zone) and movement controls within an additional 50 km surveillance zone. Animals intended to leave the restricted area must undergo vector protected quarantine for 40 days with laboratory testing as described in Annex IV to Directive 2009/156/EC . Vaccinated animals must be indelibly marked.
Member States are obliged to have contingency plans in operation and national reference laboratories must collaborate with the European Union Reference Laboratory, both in quality assurance of their diagnostic tests and vector monitoring.
African horse sickness is a notifiable disease, according to Council Directive 82/894/EEC of 21 December 1982 on the notification of animal diseases within the Community.
Click on ADNS for a description of the notification system and the latest health situation table.
The European Union Reference Laboratory for African horse sickness is:
Laboratorio de sanidad y producción animal,
Ministerio de Agricultura, Pesca y Alimentación,
28110 ALGETE, Madrid
Website: click here