Are your horses at risk for West Nile virus disease? Photo courtesy of Christinamari/Flickr.com
West Nile virus is once again being diagnosed frequently in both people and horses. According to the Center for Disease Control (CDC), the West Nile virus has been isolated in people, birds and mosquitoes in 48 states with the majority of cases coming from Texas, South Dakota, Mississippi, Oklahoma, Louisiana, and Michigan.
West Nile virus can infect horses as well as people. Horses can become infected with the disease through the bite of an infected mosquito in much the same way that people become infected.
There is currently no evidence to suggest that West Nile virus disease can be spread from horse to horse or from horses to people.
Symptoms of West Nile Virus Disease
In most cases, West Nile virus causes a mild and self-limiting disease in horses. The most commonly seen symptoms are mild fever, lethargy and lack of appetite. Most infected horses recover fully from the disease.
However, in some cases, the disease can become much more severe. Neurological symptoms such as general weakness, weakness or paralysis of the hind quarters, loss of vision or impaired vision, head pressing, circling, wandering aimlessly, seizures, difficulty swallowing, and coma can occur. The disease can be fatal for infected horses.
Treatment of Infected Horses
There is no specific cure for West Nile virus disease. As with any viral infection, treatment is supportive in nature.
Preventing Infections
There is currently a vaccine available for West Nile virus in horses. Consult your veterinarian to discuss whether your horse is at risk and whether the vaccine is recommended. Vaccinations against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE) will not protect your horse against West Nile virus as the virus belongs to a different family of viruses.
Here are some other precautions to take to help prevent infection with West Nile virus.
- Mosquitoes are most active at dusk and dawn. Keeping your horse stabled during these times will help prevent exposure to mosquitoes.
- If possible, eliminate standing/stagnant bodies of water near your horses.
- Use protective gear such as fly sheets to keep mosquitoes away from your horse.
- Apply mosquito repellents approved for use on horses.
- Place incandescent light bulbs in areas away from stalls to lure mosquitoes away.
- Fans can also help deter mosquitoes. Use fans in and around stall areas.
- Mosquitoes become infected through contact with birds. Remove any dead birds from your property. Consider contacting your local and/or state health department for help in dealing with dead birds and determining whether the bird is infected with West Nile virus.
More information about West Nile virus is provided through Pennsylvania’s West Nile Virus Control Program site.
I have personally seen the vaccination for West Nile cause symptoms in a vaccinated horse right at ten days after the live vaccine was used. Between 10 and 14 days after she fell ill, all of the horses in the pasture with her that had not been immunized the same day were sicker than I have EVER seen a horse get – and I had 70 horses for 7+ years under my care not long before that occurred.
The odds of that exact timing NOT being because the immunized horse showed symptoms due to being vaccinated and the rest of the horses being exposed to her are high enough that I believe it IS spread horse to horse.
The only horse that did not get ill was a stallion kept in a stall. Two of the horses stocked up so badly they looked like they had Purpura. They refused to move, stood with their heads down and green mucus streamed from their nostrils.
I strongly recommend against exposing unvaccinated horses to vaccinated horses. ALL horses in the pasture must either be vaccinated or quarantined away from the other horses for at least two weeks (or longer).
Horse owners must talk to every horse owner whose horses can expose theirs to make sure they are not exposed – or – even better – not share common pastures or fences with vaccinated horses.