The Virginia Department of Agriculture and Consumer Services (VDACS) has confirmed the first case of Eastern Equine Encephalitis (EEE) in a Virginia horse this year. The horse, from Suffolk, was a Saddlebred mare. She exhibited symptoms on June 22 and was euthanized June 23. Her vaccination record is unknown.
EEE causes inflammation or swelling of the brain and spinal cord. The disease is also called “sleeping sickness.” Symptoms 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.
Last year Virginia had three reported cases of EEE, one from Suffolk and two from Chesapeake. The disease has a mortality rate of 80 to 90 percent, so prevention is a key part of equine health. Vaccination and mosquito control and avoidance are the central elements of prevention.
In a press release dated March 22, 2016, VDACS encouraged horse owners to work with their veterinarians to plan a vaccination schedule that would protect their horses from EEE and West Nile Virus (WNV). Available vaccines are generally effective in drastically reducing the incidence of both EEE and WNV in horses. 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 of vaccination. The vaccines are effective for six to 12 months, so horses should be revaccinated at least annually. In an area where the disease occurs frequently, such as southeast and Tidewater Virginia, most veterinarians recommend vaccination every six months.
In addition to vaccination, it is a good idea to avoid mosquito infested areas and to take measures to reduce the local mosquito population to minimize the chances of mosquitos biting horses or humans. A horse cannot transmit EEE to a person, but the presence of infected mosquitoes in an area poses a risk to both species. Wearing protective clothing, destroying standing water breeding sites and using mosquito repellents are effective strategies for mosquito control.
For more information, please contact VDACS’ Office of the State Veterinarian at 804.692.0601 or consult your local veterinarian.