African Horse Sickness
SYMPTOMS and SIGNS
African horse sickness is not contagious. In susceptible horses, AHS usually begins with an acute fever, followed by the sudden onset of severe respiratory distress. Infected animals often stand with fore¬legs spread, head extended, and nostrils fully dilated. Other clinical signs may include rapid breathing, forced expiration, profuse sweating, spasmodic coughing, and a frothy sero¬fibrinous nasal exudate. The difficulty in breathing usually progresses rapidly, and the animal often dies within a few hours after the respiratory signs appear. In less acute cases the horse may develop extensive edema of the head neck and front legs.
CAUSES & RELEVANCE TO FLORIDA
African horse sickness is caused by an arthropod-borne virus. There are nine serotypes of the virus. It is spread by midges (Culicoides species). Mortal¬ity can be as high as 95% in some forms of this disease. Asymptomatic or mild infections may occur in zebras, African donkeys, and horses previously infected by another serotype of the virus. Dogs are susceptible to infection if they eat infected meat. African elephants have been found to carry antibodies to the virus, but there is no evidence of virus replication in this species. Zebras are considered to be the reservoir host.
African horse sickness (AHS) is endemic in sub-Saharan central and east Africa. This dis¬ease often spreads to southern Africa and occasionally to northern Africa. Outbreaks have been seen in Egypt and other parts of the Middle East, as well as in Spain. The disease has never been recorded in North America.
Similar to the situation with West Nile virus, insect vectors already exist in the USA that are considered capable of transmitting AHS virus. The related virus of bluetongue is transmitted in Florida by several species of Culicoides. Bluetongue is a hemorrhagic disease that affects sheep and deer and was probably introduced to the USA in the 1930’s. The widespread distribution of bluetongue virus in the livestock of Florida indicates that the introduction of AHS virus to the state could rapidly lead to an extensive epidemic that would be a disaster for the various sectors of the equine industry. The greatest danger to Florida probably exists through the inadvertent importation from Africa of a reservoir species of AHS virus. Currently the zebra is considered the reservoir species, but the epidemiology of AHS is not fully understood and it is possible that other wild animal species are unidentified.
Location: http://epi.ufl.edu/animal/africanhorse.shtml