Animal Diseases - Control Measuresslide


Description - Control measures


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. 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.

All serotypes of AHS virus occur in eastern and southern Africa; this distribution reflects that of zebra, which cycle the virus asymptomatically. In West Africa only AHS serotype 9 is 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.

Control measures

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 D of Directive 90/426/EEC. Vaccinated animals must be indelibly marked.

Member States are obliged to have contingency plans in operation and national reference laboratories must collaborate with the Community Reference Laboratory, both in quality assurance of their diagnostic tests and vector monitoring.



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