COLUMBIA — Dr. Boyd Parr, South Carolina State Veterinarian and director of Clemson University Livestock Poultry Health, today announced the first confirmed case of Eastern Equine Encephalitis (EEE) in a horse for the state this year. A foal from Sumter County that died recently tested positive for the disease. Two adult horses that died at the same farm around the same time are suspected of also having EEE, a serious, mosquito-borne illness in horses that can also affect humans.

EEE is preventable by vaccinating horses. The State Veterinarian urges horse owners to consult with their veterinarians to be sure vaccinations against both EEE and West Nile Virus (WNV) are up-to-date. 

“This diagnosis is a vivid reminder of the threat that mosquito-borne diseases represent to horses in our state.” said Dr. Parr. “Maintaining protection by vaccinating horses is important again this year.” During 2012, there were 14 confirmed cases of EEE and 7 of WNV in South Carolina.

The EEE virus is maintained in nature through a cycle involving the freshwater swamp mosquito Culiseta melanura, commonly known as the blacktailed mosquito. Two to three days after becoming infected with EEE virus, a mosquito becomes capable of transmitting the virus. Infected mosquitoes that feed on both birds and mammals can transmit the disease to horses and humans.

Symptoms usually develop in horses from 2 to 5 days after exposure. Symptoms of EEE virus in horses include stumbling, circling, head pressing, depression or apprehension, weakness of legs, partial paralysis, the inability to stand, muscle twitching or death. Nine out of every 10 horses infected with EEE virus dies from the disease.

Any livestock (including horses) that display neurologic signs (stumbling, circling, head pressing, depression or apprehension) must be reported to the state veterinarian at 803-788-2260 within 48 hours, according to the state law.