Mosquito-Borne Diseases in Equine

— Written By Chris Jeffcoat

We’re now in mosquito season and recent heavy rains have created conditions favorable to mosquito breeding. Therefore, equine owners should talk to their veterinarians about protecting their animals from mosquito-borne diseases through vaccinations.

 West Nile virus (WNV) and Eastern Equine Encephalomyelitis (EEE) are endemic across North Carolina and can cause illness or death, but they can be prevented with a sequence of two vaccines.

 In 2012, there were twenty confirmed cases of EEE and three cases of WNV, but state officials say they expect up to four unreported cases for each one confirmed, making the possible impact much larger. As of July 26, 2013, there have been three cases of EEE in North Carolina this year.

 “North Carolina has an extended mosquito breeding period, so every horse owner should talk to their veterinarian about how to protect their animal year-round,” State Veterinarian David Marshall said. “In addition to getting animals vaccinated, everyone needs to be extra vigilant now to reduce the breeding grounds for mosquitoes. Take the time to rid your yard and pasture of any standing water to reduce the risk.”

 The EEE and WNV vaccinations initially require two shots, three to four weeks apart, for horses, mules and donkeys that have no prior vaccination history. Neither vaccination fully protects your animal until several weeks after the second shot, so it is best to vaccinate as early in the mosquito season as possible.

 Symptoms of EEE include impaired vision, aimless wandering, head pressing, circling, inability to swallow, irregular staggering gait, paralysis, convulsions, and death. Symptoms of WNV in horses can include loss of appetite and depression, fever, weakness or paralysis of hind limbs, convulsions, impaired vision or hyper-excitability. There is no evidence that horses can transmit the virus to other horses, birds or people through direct contact.

 For more information, please contact Chris Jeffcoat, Stokes and Forsyth County Area Extension Agent for Livestock, 336-528-0210. This article was adapted from an article originally written by Dr. Tom Ray, NCDA&CS Director of Livestock and Health Programs.