“Mosquito-breeding season in North Carolina lasts from spring until the first frost and horses are at risk if not properly vaccinated,” Troxler said. “EEE is fatal 90% of the time in horses and WNV has a fatality rate of 30 percent. However, both diseases are preventable by vaccination.” 

So far this year we have had no cases of EEE or WNV, but last year there were seven cases of EEE, Troxler added. 

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 WNV or EEE. 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 repellants can be effective if used according to the manufacturer’s instructions. 

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 symptoms to appear. 

Symptoms of WNV include fever, weakness or paralysis of hind limbs, impaired vision, head pressing, seizures and aimless wandering.  

People, horses and birds can become infected from a bite by a mosquito carrying these diseases, but there is no evidence that horses can transmit the viruses to other horses, birds or people through direct contact.