COLUMBIA — South Carolina’s state veterinarian Friday announced that two cases of Eastern Equine Encephalitis (EEE) have been confirmed in the state. A horse that died in Darlington County and a miniature donkey that died in Horry County recently tested positive for the disease.


Horses should be vaccinated to prevent infection with Eastern Equine Encephalitis.

Eastern Equine Encephalitis is a serious, mosquito-borne illness in horses that can also affect humans. Vaccination can prevent the disease in horses.

“Horse owners should check with their veterinarian to be sure their horses’ vaccinations are up to date against both EEE and West Nile Virus,” said Boyd Parr, state veterinarian and director of Clemson University Livestock-Poultry Health (LPH). “Vaccination is especially important in our coastal counties.”

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,” said Adam Eichelberger, veterinarian overseeing LPH animal health programs. “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. The symptoms 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 die from the disease. In South Carolina last year, 48 of the 49 of the confirmed cases died from the EEE infection. South Carolina led the nation in EEE cases.

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