State veterinary officials are urging South Carolina horse owners to vaccinate their animals following the discovery of an unusually early case of Eastern equine encephalitis (EEE) in a Horry County horse.

“This is the earliest in the spring that we’ve seen this disease in many years,” said Adam Eichelberger, DVM, Dipl. ACT, who oversees the animal health programs for Clemson University Livestock-Poultry Health. The horse was euthanized.

Eastern equine encephalitis is a serious, mosquito-borne illness that can also affect humans. In unvaccinated horses, it is almost always fatal.

“Nine of 10 exposed, unvaccinated horses will succumb to the disease,” said Eichelberger. “However, with proper vaccine use the risk of disease is minimized