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Horses: What Owners Need To Know About West Nile Virus

Updated on June 16, 2011

Vaccinating your horses for the West Nile Virus is a proven way to protect them, at least in my mind. This summer I moved to a new home that had an overgrown ditch near the house and pasture. A perfect breeding ground for mosquitoes who carry the virus. We hadn't lived there 2 months when I contracted West Nile Virus. My horses, being vaccinated, did not. The neighbor's daughter's horse, who hadn't been vaccinated, wasn't so lucky. Ultimately her horse had to be put down as it's hind legs became paralyzed. It can be a horrible death for your treasured friend, but with a little effort can be prevented.

West Nile Virus or (WNV) is a viral disease not seen in the United States until 1999. The disease originated in Asia, Africa, and Southern Europe. If infected WVN can cause encephalitis or meningitis. Both of which infect the spinal cord and the brain of the horse.

Horses are infected with West Nile Virus by a mosquito bite. Mosquitoes become infected with the virus after they have feed on birds that are infected. Many types of birds can be infected with the virus, and if you find a dead bird on your property you should contact your local Fish and Game office to report it.

The number of horses infected with West Nile Virus is on the rise in all states. Especially hard hit in 2007 were Oregon, California, Arizona and New Mexico. A total of 503 cases of West Nile Virus in horses were reported as of March 4, 2008.

Cumulative 2007 Data as of March 04, 2008. National Cumulative Veterinary Disease Cases: 503

These data are provisional and may be revised or adjusted in the future. For further information or questions regarding the above data contact the Centers for Disease Control and Prevention:

Signs and Symptoms of West Nile Encephalitis in Horses

Horses are prone to severe WNV infection. Severe symptoms of WNV in horses can develop as fever, weakness and in extreme cases, paralysis of hind limbs, muscle fasciculation's or muzzle twitching, ataxia (in-coordination), convulsions, hyper-excitablity, or even coma. They can also experience head pressing, aimless wandering, and inability to swallow. In extreme cases it may also result in death. Once a horse has been infected the incubation period is usually 15 days. It has not been found that horses who become infected with the virus can transmit the virus to humans.

Treatment for West Nile Virus in Horses

There is no specific treatment. Supportive veterinary care is recommended. However, if your horse suffers severe symptoms such as paralysis of hind limbs, it may be something you want to discuss with your veterinarian, as their full recovery, in most cases, is unlikely.


There are currently four vaccines for horses. After the initial series of vaccinations you should have your horse vaccinated yearly with a booster shot in April. For horses who are in high stress situations such as show horses or racehorses should receive a booster shot in April and July. The only way that your horse will truly be protected is by having them vaccinated. Other vaccines for encephalitis will not protect against the West Nile Virus.

Horses that are infected with the virus are not shown to be able to transmit the disease to other horses. It is best, however, if you suspect a horse to have the virus separate them from others as soon as possible. While other viruses can cause some of the same symptoms it is still wise to see your veterinarian to be certain.

While there are several things you can do to prevent a possible mosquito bite on your horse, the only way to be sure is to have them vaccinated each year. From the yearly increase in reported cases the treat of WNV is not going away any time soon.


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    • GmaGoldie profile image

      Kelly Kline Burnett 7 years ago from Madison, Wisconsin

      The skin problem called "scratches" for horses is a fungus as I understand. I didn't realize that horses were susceptible to the WNV. I learned allot - complete with four different vaccines.

    • sharkarama profile image

      sharkarama 8 years ago

      wow, I never really thought about other animals getting diseases like west nile virus. Thanks for sharing.

    • Uriel profile image

      Uriel 9 years ago from Lebanon

      The information displayed shows a great deal of care to your horses. this WNV sounds like a horrible disease poor horses. I am really glad you shared this information with us.Thanks