RALEIGH — A 2-year-old mare from Robeson County is one of two quarter horses euthanized this month after contracting Eastern Equine Encephalomyelitis, a mosquito-borne disease that is preventable in equine by vaccination.

Both horses were unvaccinated and exhibited signs of generalized weakness, stumbling, depression and inability to stand or eat. The other was a stallion from Bladen County.

According to the state Department of Agriculture and Consumer Service’s veterinary division, they are the first reported cases of EEE in horses this year. Last week, New Hanover County officials reported that EEE was found in a sentinel chicken flock.

“If your horses exhibit any symptoms of EEE, contact your veterinarian immediately,” said State Veterinarian David Marshall. “Several serious contagious diseases, such as Equine Herpes Virus and rabies, have similar symptoms and should be ruled out.”

EEE causes inflammation or swelling of the brain and spinal cord and is often fatal. Symptoms of EEE include impaired vision, aimless wandering, head pressing, circling, inability to swallow, irregular staggering gait, paralysis, convulsions and death. Once a horse has been bitten by an infected mosquito, it may take three to 10 days for signs of the disease to appear.

In Robeson County, the horse deteriorated so quickly that it was euthanized within 24 hours of first exhibiting symptoms. The Bladen County horse had symptoms for several weeks before being euthanized.

Marshall recommends that owners talk to their veterinarians about an effective vaccination protocol to protect horses from EEE and another mosquito-borne disease, West Nile Virus. The EEE and West Nile vaccinations initially require two doses for horses, mules and donkeys that have no prior vaccination history.

Mosquitoes can breed in any puddle that lasts for more than four days, so removing any source of standing water can reduce the chance of exposing animals to the diseases.

Keeping horses in stalls at night, using insect screens and fans and turning off lights after dusk can also help reduce exposure to mosquitoes. Insect repellents can be effective if used according to manufacturers’ instructions.

There is no evidence that horses can transmit the virus to other horses, birds or people through direct contact.