African horse sickness virus (AHSV) is an orbivirus in the Reoviridae family that causes African horse sickness (AHS), a fatal re-emergent vector-borne disease of horses. The virus is similar to other orbiviruses which include bluetongue virus (BTV) and equine encephalosis virus (EEV). African horse sickness is endemic to sub-Saharan Africa; however, important outbreaks have occurred in North Africa, the Iberian Peninsula, the Middle East and the Indian subcontinent, causing up to 95% mortality. There are nine different serotypes of AHSV identified. The virus has a 10-segmented genome of double-stranded RNA contained within a non-enveloped triple-layer capsid. The virion is non-enveloped and has an approximate size of 55–70 nm.
AHSV is transmitted by Culicoides midges. Laboratory confirmation of clinical suspicion is made by the detection of AHSV in blood or post-mortem tissues through the use of classical virus isolation (VI), immuno-histochemistry, antigen detection ELISA techniques (based on protein VP7), and recently a AHSV RT-LAMP assay was developed.