[1] First described in South Africa over a hundred years ago by Arnold Theiler, EEV is the causative agent of equine encephalosis (EE), an arthropod-borne disease transmitted by the Culicoides spp.

[4] Elevated heart and respiratory rates are also common, and occasionally as a result of nasal congestion, a red-brown discolouration of the mucous membranes may be observed.

[4] Although rare, more severe clinical signs may occur including facial swelling (lips and eyelids), respiratory distress, and petechial haemorrhages of the conjunctivae.

[5] As of 2008 however, evidence seems to suggest the virus has circulated beyond southern Africa, and outbreaks have been reported in a number of other countries including Israel, Ethiopia, Ghana, and Gambia.

[5] Such a progression is of major concern to the worldwide livestock industry, primarily due to the similarity between EEV and other more devastating equid pathogens, such as the African horse sickness virus.

[4] Several studies have shown that between 50 and 75% of South African equids (notably horses, donkeys and zebras) are seropositive for EEV or have anti-EEV antibodies indicating a prior infection, with serotype 1 being the most prevalent.

Control of the midges is usually only instigated for domesticated stabled horses, and includes precautionary measures such as the limited use of lights at night, as well as the use of fly repellents and fans.