CLEMSON, S.C. (WSPA) – Two SC horses have died as a result of a mosquito-borne illness.

A two-year-old quarter horse gelding in Sumter County and a five-year-old quarter horse mare in Lee County died after catching Eastern Equine Encephalitis, according to State Veterinarian Michael J. Neault, director of Clemson Livestock Poultry Health.

These are the first known cases of the illness this summer. However, another case was confirmed in a horse in Berkeley County in mid-January.

Neault reminded horse owners of the importance of vaccinating their animals against Eastern Equine Encephalitis and other diseases, like West Nile Virus and rabies.

“We had some heavy rains in areas across the state over the last month which means that mosquito populations can be extremely high,” Neault said. “It is always important for horse owners to stay on top of equine vaccination schedules, but it is essential now considering the rain we’ve had.”

Mosquito control is also an important precaution, as both Eastern Equine Encephalitis and West Nile Virus are borne by mosquitos and have high mortality rates in unvaccinated horses.

Symptoms of Eastern Equine Encephalitis usually develop two to five days after exposure and include stumbling, circling, head pressing, depression or apprehension, weakness of the legs, partial paralysis, inability to stand, muscle twitching, and death.

Any livestock that display neurological symptoms like these must be reported to the state veterinarian at (803) 788-2260 within 48 hours.