West Nile Virus

Updated March 2018 

Since first being recognized in the United States in 1999, West Nile virus (WNV) has posed a serious threat to horses and humans alike. In the equine population, the virus is transmitted when a mosquito takes a blood meal from a bird infected with WNV, then feeds on a horse. 

While many horses exposed to WNV experience no signs of illness, the virus can cause inflammation of the brain and spinal cord. In some cases, especially in older horses, WNV can be fatal. 

As a horse owner, prevention is the key to reducing your horse’s risk of contracting WNV. Follow these guidelines from the American Association of Equine Practitioners (AAEP) to protect your horse against WNV: 

1. Vaccinate your horse against the disease with one of the available vaccines. Talk with your veterinarian about the most appropriate vaccination schedule for your horse. 

2. Eliminate potential mosquito breeding sites. Dispose of old receptacles, tires and containers and eliminate areas of standing water. 

3. Thoroughly clean livestock watering troughs at least monthly. 

4. Use larvicides to control mosquito populations when it is not possible to eliminate particular breeding sites. Such action should only be taken, however, in consultation with your local mosquito control authority. 

5. Keep your horse indoors during the peak mosquito activity periods of dusk to dawn. 

6. Screen stalls if possible or at least install fans over your horse to help deter mosquitoes.

7. Avoid turning on lights inside the stable during the evening or overnight. 

8. Using insect repellants on your horse that are designed to repel mosquitoes can help reduce the chance of being bitten. 

9. Remove any birds, including chickens, located in or close to a stable. 

10. Don’t forget to protect yourself as well. When outdoors in the evening, wear clothing that covers your skin and apply plenty of mosquito repellent. 

For more information about the virus, consult your equine veterinarian. 

The American Association of Equine Practitioners, headquartered in Lexington, Ky., was founded in 1954 as a non-profit organization dedicated to the health and welfare of the horse. Currently, AAEP reaches more than 6 million horse owners through its nearly 10,000 members worldwide and is actively involved in ethics issues, practice management, research and continuing education in the equine veterinary profession and horse industry.