Vaccinate horses now to lower risk of mosquito-borne illnesses

Published 2:47 pm Wednesday, April 3, 2019

Spring has sprung in Virginia, and as temperatures rise, so does the risk of mosquito-borne illnesses. The Virginia Department of Agriculture and Consumer Services (VDACS) encourages horse owners to talk to their veterinarians about vaccinating their horses for West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE). In 2018, Virginia had two cases of confirmed WNV in a horse and eight cases of confirmed EEE.

“The mortality rate for WNV is 30 percent and up to 90 percent for EEE. Vaccinations for WNV and EEE are highly effective in minimizing disease, if given appropriately,” said Dr. Charlie Broaddus, VDACS State Veterinarian. “The vaccines are effective for six to 12 months, so horses should be re-vaccinated at least annually. In areas where the disease occurs frequently, most veterinarians recommend vaccination every six months. For the vaccine to be effective, it must be given at least two weeks before the horse is exposed to the virus. To stimulate full immunity, horses must be vaccinated twice, about 30 days apart, during the first year of vaccination.”

Humans cannot become infected with EEE or WNV by handling an infected horse, nor can a horse acquire the virus directly from another infected horse. The presence of an infected horse in the area indicates that mosquitoes carrying EEE or WNV are present, and those insects pose a threat to both humans and horses.

Horse owners should contact their veterinarian to schedule the WNV and EEE vaccination. Other prevention methods include dumping or draining standing water breeding sites for mosquitoes, such as containers and puddles; using insect repellents and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn, and turning off the lights in and around the barn at night.
For more information on WNV or EEE, contact the VDACS Office of Veterinary Services at (804) 786.2483 or go to