Ask the Vet

Large Animal

Spring 2004



Dr. Dale Shilling
Equine Clinic
Ambler, PA
Dr. Shilling is a well-known area equine vet. He has been practicing in the Philadelphia region for 25 years, and is favored among local riders and organizations regarding information support!



Since first being recognized in the United States in 1999, West Nile Virus has posed a serious threat to horses and humans. In the equine population the virus is transmitted by a mosquito taking a blood meal from a bird infected with WNV, then feeding on a horse. Many horses exposed to WNV by a mosquito carrying the virus experience no clinical signs of illness.

However, the virus can cause inflammation of the brain and spinal cord resulting in a generalized weakness (seen in both front and rear legs), muscle twitching, depression, increased heart and respiratory rates and can be fatal.

As a horse owner, prevention is the key to reducing your horseís risk of contracting WNV, The following are guidelines for the AAEP to protect your horse from WNV:

1) Safe and effective vaccine (April to August)
2) Eliminate mosquito breeding sites. Dispose of old
receptacles, tires and containers. Eliminate standing water.
3) Clean livestock watering troughs at least monthly.
4) Use larvicides or minnows to control mosquito
populations when you canít eliminate breeding sites.
5) Keep horse indoors during peak periods (dusk and dawn).
6) Screen stall, or at least install fans to deter mosquitoes.
7) Avoid turning on barn lights in evening or overnight.
8) Use mosquito-repellent insect repellant on your horses.


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