Written by the AAEP

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:

• Consider vaccinating your horse against the disease.  In February 2003, a vaccine was licensed by the United States Department of Agriculture’s Center for Veterinary Biologics for use in healthy horses as an aid in the prevention of the disease.  Talk with your veterinarian about the most appropriate vaccination schedule for your horse.

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

• Thoroughly clean livestock watering troughs at least monthly.

• 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.

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

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

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

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

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

• 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, ask your equine veterinarian for the “West Nile Virus” brochure, produced by the AAEP in conjunction with Bayer Animal Health, an AAEP Educational Partner.  Additional information about WNV can be found on the AAEP’s horse-health Web site, www.myHorseMatters.com.

Reprinted with permission from the American Association of Equine Practitioners.