West Nile Virus can affect humans, horses, and many types of birds. It is carried by mosquitoes, which become carriers by feeding on infected birds. West Nile Virus has been found in Oregon, where it has affected both the equine and human populations.

West Nile Affects Equines More Than Other Animals
Symptoms include: loss of appetite, loss of coordination, confusion, fever, stiffness, muscle tremors, and weakness. About one-third of horses that become ill from the West Nile Virus will die. However, it is important to note that most horses that are exposed to West Nile Virus do not become ill (they do not show clinical signs).

Minimize the Threat of Exposure
The best way to minimize the threat of West Nile virus to your horses-- and to yourself--is to control mosquito populations and prevent exposure to them. Eliminate sources of standing water that can serve as a breeding ground for mosquitoes, including old tires, buckets, and other containers. Change water in troughs weekly. Use forced air fans in barns to keep mosquitoes at bay.

Now is the Time to Immunize 
The vaccine requires two doses given three to six weeks apart. Immunity may not be achieved until up to six weeks after the second dose, and some horses may require a third vaccination. An annual booster should be given prior to the start of the mosquito season in your area.

Consult your veterinarian for more information on immunizing your horses. You can protect them from this virus.

The Oregon Veterinary Medical Association is a nonprofit organization of veterinarians who are dedicated to helping people give their animals a high quality of life.