African horse sickness

African horse sickness (AHS) is a highly infectious and deadly disease that affects horses, mules, and donkeys, as well as dogs and camels. It is caused by the African horse sickness virus (AHSV), a double-stranded RNA virus of the genus Orbivirus. The disease is transmitted by the bite of infected Culicoides midges and is characterised by respiratory and circulatory damage.

Epidemiology

AHS is endemic in Sub-Saharan Africa, but outbreaks have been reported in other parts of the world, including the Middle East and Europe. The disease is not directly contagious, but is spread by the bite of infected Culicoides midges. These insects are most active during warm, wet weather, and outbreaks often occur during the rainy season.

Clinical signs

The clinical signs of AHS vary depending on the form of the disease. The pulmonary form is characterised by fever, coughing, nasal discharge, and severe difficulty breathing. The cardiac form is characterised by swelling of the eyes and head, and heart failure. The mixed form shows signs of both the pulmonary and cardiac forms. In all forms, death can occur within a few days of the onset of symptoms.

Diagnosis

Diagnosis of AHS is based on clinical signs, post-mortem findings, and laboratory tests. The virus can be detected in blood, tissue samples, or post-mortem specimens using techniques such as virus isolation, polymerase chain reaction (PCR), and enzyme-linked immunosorbent assay (ELISA).

Treatment and control

There is no specific treatment for AHS. Management of the disease involves supportive care, including rest, hydration, and treatment of secondary infections. Vaccination is the most effective method of control. The current vaccine is a live attenuated vaccine, but research is ongoing to develop safer and more effective vaccines.

Impact

AHS has a significant impact on the equine industry, particularly in endemic areas. Outbreaks can result in high mortality rates, trade restrictions, and significant economic losses.