Review on African Horse Sickness

Abstract

African Horse Sickness (AHS) is a disease that commonly affects equines. The disease is known to be spread by insect vectors (insect-borne) caused by African Horse Sickness Virus (AHSV) in the family Reoviridae genus Orbivirus. The genome of an AHSV comprises 10 segments of linear dsRNA, encoding seven structural (four major and three minor) and five non-structural proteins. The most common hosts of the diseases are horses, mules, donkeys, and zebras where zebras are natural reservoir host and play vital role in the persistence of the virus. There are four known clinical forms of African horse sickness: pulmonary, cardiac, mixed, and horse sickness fever (mild) forms. The clinical signs and lesions aligned with previous epidemiological information might be enough for clinical diagnoses of African horse sickness virus. But, the clinical signs and lesions showed for AHS can be confused with other disease, Equine Encephalosis Virus (EEV) as both viruses are similar, have a similar geographical distribution, host range and the same vector species. Thus diagnosis of AHSV can be confirmed from whole blood collected in anticoagulant in the febrile stage of infection and other tissues using RT-PCR, cell culture and sandwich ELISA. There is no an exact and specific treatment for animals suffering from AHS. Secondary infections must be treated during the recovery period with antibiotic. The disease is non-contagious and can only be spread through the bites of infected vector species of Culicoides. Control may therefore be effective by: animal movement restrictions, Slaughter of viraemic animals, Husbandry modification, Vector control and Vaccination.