Equine African Horse Sickness Study Guide

Overview and Clinical Importance

African Horse Sickness (AHS) is a highly infectious, non-contagious, arthropod-borne viral disease of equids that is endemic to sub-Saharan Africa. It is caused by the African Horse Sickness Virus (AHSV), an Orbivirus of the family Reoviridae. AHS is characterized by respiratory and circulatory impairment with mortality rates reaching up to 95% in naive horses. The disease is listed as a notifiable disease by the World Organisation for Animal Health (WOAH/OIE) due to its severity and potential for rapid global spread.

AHS has significant economic consequences for the equine industry, affecting international horse trade, sporting events, and equestrian activities. Climate change and the expanding geographic distribution of Culicoides midge vectors have raised concerns about potential outbreaks in previously AHS-free regions including Europe and North America.

Etiology

Causative Agent

African Horse Sickness Virus (AHSV) is a member of the genus Orbivirus within the family Reoviridae. The virus is closely related to Bluetongue Virus (BTV), another Orbivirus that affects ruminants.