July 1, 2013 — In a news release on June 28, South Carolina State Veterinarian and Director of Clemson University Livestock Poultry Health Dr. Boyd Parr announced confirmation of the first case of Eastern equine encephalitis (EEE) in a South Carolina horse this year. A foal from Sumter County died, then tested positive for the disease. Two adult horses that died at the same farm around the same time are suspected of having EEE.

Clemson University noted that EEE is a serious, mosquito-borne illness in horses that can also affect humans. EEE is preventable by vaccination in horses.

“South Carolina horse owners are urged by the state veterinarian to consult with their veterinarians to be sure vaccinations against both EEE and West Nile virus (WNV) are up-to-date,” noted the release.

Parr was quoted as saying: “This June diagnosis of EEE is a vivid reminder of the threat of EEE and other mosquito borne diseases to horses in our state. Maintaining protection of horses through vaccination is again important this year. During 2012, there were 14 confirmed cases of EEE and seven 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, noted the report. Two to three days after becoming infected with the 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 two to five days after exposure.

Symptoms of EEE virus in horses includes stumbling, circling, head pressing, depression or apprehension, weakness of legs, partial paralysis, the inability to stand, muscle twitching or death. Nine out of 10 horses infected with EEE virus will die 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 South Carolina state law.