State Vet: It Makes Sense to Vaccinate Most Horses Now

~ State Veterinarian’s Office encourages horse owners to check with their veterinarians now regarding vaccination schedule ~animal-brown-horse

Mosquito season will begin soon in Virginia. That means it’s time to start thinking about vaccinating your horses against mosquito-borne illnesses such as West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE). The Virginia Department of Agriculture and Consumer Services (VDACS) encourages all horse owners to check with their veterinarians for vaccination recommendations for their animals. In 2016, Virginia had seven confirmed cases of EEE in horses.

“Both the WNV and EEE vaccine have proven to be highly effective in minimizing disease, if given appropriately,” said Dr. Charles Broaddus, State Veterinarian at VDACS. “Without vaccination, we would see many more infected horses, so we encourage horse owners vaccinate against EEE and WNV. In most cases, private veterinarians will recommend them for their clients.”

WNV and EEE vaccines are effective for 6-12 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 handled and administered properly and be given at least two weeks before the horse is exposed to the virus. Additionally, to stimulate full immunity, horses must be vaccinated twice, about 30 days apart, the first year they are vaccinated.

Other prevention methods include dumping or draining standing water breeding sites (e.g. containers and puddles) for mosquitoes, 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.

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 the EEE or WNV viruses are present, however, and those insects pose a threat to both humans and horses.

Both EEE and WNV cause neurologic signs in horses, such as  staggering, circling, depression, loss of appetite and sometimes fever and blindness. The mortality rate with WNV is 30 percent, but up to 90 percent with EEE. There is no proven cure for these diseases, but veterinarians can provide supportive therapy to treat symptoms of EEE and WNV and keep horses from injuring themselves.

When horse owners call the vet about a vaccination schedule, it’s also a good time to get the horse tested for Equine Infectious Anemia (EIA) with a simple blood test known as the Coggins test. According to Virginia law, all horses assembled at a show, fair, race meet or other such function or participating in any activity on properties where horses belonging to different owners may come into contact with each other in Virginia must be accompanied by a report of an official negative test for equine infectious anemia.

For more information on WNV, EEE or the Coggins test for EIA, contact the VDACS Office of Veterinary Services at 804.786.2483 or see

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