AFRICAN HORSE SICKNESS (AHS)
Definition: Highly fatal, insectborne viral disease endemic to sub-Saharan countries.
Causes: AHS is caused by infection with one of nine strains (serotypes) of a virus in the Reoviridae family. Two insect vectors, both of which are biting midges, are known to carry the virus: Culicoides imicola and Culicoides bolitinos. The disease is transmitted between horses, mules, donkeys and zebras through the bites of these insects, peaking during warm months of the year when insects are most active. Zebras are thought to be reservoir hosts, meaning they harbor the virus for long periods of time without becoming significantly ill.
Signs: There are three types of AHS: A cardiac form, which leads to swelling in the depressions just above the eyes, along with the head, neck, throat and shoulder, in addition to a fever between 102 and 106 degrees Fahrenheit; a respiratory form, characterized by difficulty breathing, coughing, a frothy discharge from the nostrils and a fever of 104 to 106 degrees Fahrenheit; and a “mixed” form with characteristics of both. The mortality rate is between 50 and 90 percent depending on the form of the disease and severity of the case; horses typically die within a week of onset of illness.
Diagnosis: The only conclusive test for AHS requires detecting the virus in a blood sample, which can take several days. Due to the fast-moving nature of the disease, most diagnoses are made on clinical signs alone, taking into account environmental factors such as insect activity and weather patterns.
Treatment: Intravenous fluids and other supportive care. Nonsteroidal anti-inflammatory medications and corticosteroids are used to address the fever and other clinical signs. Antibiotics may be administered to prevent secondary bacterial infections, particularly in respiratory cases. Horses may also be given intravenous fluids.
BITING MIDGE ( CULICOIDES IMICOLA)