The Virginia Department of Agriculture and Consumer Services (VDACS) today announced the second case of Eastern Equine Encephalitis (EEE) in a Virginia horse this year. The horse, a thoroughbred, was from Suffolk. The horse had been vaccinated and is recovering. Without vaccination the mortality rate is 80 to 90 percent.
VDACS received confirmation of the diagnosis from the National Veterinary Services Laboratory in Ames, Iowa on July 8. Virginia also has had one other case of EEE this year, also from Suffolk. In this part of the state veterinarians usually recommend a six-month vaccination interval.
“One of the reasons most veterinarians recommend a six-month vaccination schedule in Tidewater Virginia is because of the prevalence of mosquitos in the area,” said Dr. Charles Broaddus, State Veterinarian. He explained that EEE, a mosquito-borne illness, causes inflammation or swelling of the brain and spinal cord and 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 high mortality rate, so prevention is a key part of equine health. Vaccination and mosquito control/ avoidance are the central elements of prevention. Available vaccines are generally effective in drastically reducing the incidence of both EEE and West Nile Virus (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 addition to vaccination, horse owners should avoid mosquito infested areas and take measures to reduce the local mosquito population to minimize the chances of mosquitos biting people and their horses.