April 20, 2010
The Virginia Department of Agriculture and Consumer Services (VDACS) urges all horse owners to ask their veterinarians for West Nile Virus and Eastern Equine Encephalitis vaccination recommendations for their animals.
There were an increased number of Eastern Equine cases in Virginia in 2009, but the number of equine West Nile cases dropped in comparison to the last couple of years, and state officials are concerned that horse owners may be lulled into inaction by the lack of disease activity.
“We have had some unusual weather patterns in the last year, including heavy rain over much of the state.” says Dr. Joseph Garvin, Program Manager for VDACS’ Office of Laboratory Services. “How that affects the overall mosquito population as well as levels of [Eastern Equine] and [West Nile] viruses in those mosquitoes is hard to predict. The bottom line is, these vaccines are very safe and effective, and we believe that in most cases, private veterinarians will recommend them for their clients. Horse-owners need to be aware that the vaccines require boosters every six to twelve months.”
Vaccines are available to drastically reduce the incidence of these diseases in horses. The vaccines are effective for six - twelve months, so horses should be re-vaccinated at least annually. In an area where the disease occurs frequently, such as southeast and Tidewater Virginia, 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 that the horse is vaccinated. Other prevention methods include destroying standing water breeding sites for mosquitoes, using insect repellents and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn.
Typical symptoms of encephalitis in equines include staggering, circling, depression, loss of appetite and sometimes fever and blindness. There is no cure for these diseases, which can kill anywhere from 30 percent (West Nile) to 90 percent (Eastern Equine) of the horses infected. Humans cannot become infected by handling an infected horse, nor can a horse acquire the virus from another infected horse; however, the presence of an infected horse in the area indicates that mosquitoes carrying Eastern Equine or West Nile are present and pose a threat to both humans and horses.
Horse owners should contact their veterinarians for further advice on prevention, diagnosis and treatment. For more information, contact the Office of the State Veterinarian, Division of Animal Industry Services, VDACS, at 804.786.2483.