According to the Food and Agriculture Organization of the United Nations, transboundary animal diseases that were originally confined to tropical countries are on the rise around the world.
African Horse Sickness is a devastating insect-transmitted viral disease of horses that has been endemic to Saharan Africa and occurs extensively throughout much of South Africa.
African Horse Sickness is transmitted by the blood-sucking insect Culicoides, (a small fly). Culicoides insects are abundant on all continents except Antarctica, but to date just two of the 1300+ species have proven to be competent vectors of AHS virus.
One form of AHS which affects the lungs of horses is characterized by very high fever, difficulty breathing, frothy discharge from the nose, and sudden onset of death. The mortality rate is about 90 percent.
Another form, the cardiac form is characterized by fever followed by swelling of the head and eyes, an inability to swallow, bleeding in the membranes of the mouth and eyes, and a slower onset of death occurring four to eight days after the onset of fever. The mortality rate for the cardiac form of African Horse Sickness has been estimated at around 50%.
Because of its devastating effects, AHS is on the list of economically important equine diseases worldwide and is reporting is required to local and international officials including the OIE, the animal equivalent of the World Health Organization.
Outbreaks of AHS have occurred regularly in southern Africa for several centuries. Periodically AHS has occurred in North Africa, the Mediterranean Basin the the Middle East. An incursion into Spain in the late 1980's complicated planning for equestrian events at the 1992 Olympics in Barcelona.
So far, no cases of African Horse Sickness have occurred in the United States, but some scientists predict that the disease may move into the temperate zones including Europe, the United States and Australia based on the movement of such diseases as West Nile virus and Bluetongue virus.