- Pets and Animals
Horse Disease Focus - West Nile
West Nile Virus
The West Nile virus originated in eastern Africa, but is now endemic throughout the United States. It affects multiple species, including equines and humans.
The good news is that many horses that catch the West Nile virus show no signs of illness and recover on their own. You may well not know your horse ever caught the disease, and an animal can only have West Nile once.
If the horse does become ill, though, the first symptom is generally appetite loss and overall lethargy. Its temperature will be elevated. The disease can also cause central nervous symptoms, especially weakness or paralysis of hind limbs and impaired vision. Behavioral changes have been observed, including aimless wandering, walking in circles and irritability or excitability. Some horses experience difficulty swallowing.
West Nile can be fatal in horses, although this is rare. Fatalities usually occur in very old or very young animals, or those with compromised immune systems.
There is no specific treatment for West Nile. Nursing and supportive care is generally recommended, focusing on getting the horse's temperature down. Given the risk of behavioral changes, the horse should be confined to a stall or a small paddock, on its own, to reduce its chances of injuring itself or others.
Most horses make a full recovery. West Nile is not contagious between horses or between horses and humans, so there is no need to isolate the horse, although if it has neurological symptoms it should be kept away from other horses for its own safety.
A blood test should be used to confirm West Nile and steps should be taken to reduce mosquito numbers in the area.
An equine vaccine is available to protect against West Nile, although it is fairly new. The vaccine should be administered annually a few weeks before mosquito season starts. As yet there is no vaccine available for humans.
The best way to control West Nile is to control mosquitos. Drain standing water and cover rain barrels with mosquito netting. The only water containers full on your property should be ones horses are actively drinking from. Don't leave wheelbarrows upright...always store them upside down or against a wall (This also helps keep them clean). If you have an ornamental pond, the best preventive is to put a few fish in there - fish will eat mosquito eggs and larva.
The other primary reservoir for the virus is certain wild birds. Specifically, corvids, jays and raptors are considered likely to be affected. It is best, therefore, not to encourage these birds to nest on your property. Any dead birds should be disposed of immediately. However, do not discourage insectivorous birds such as barn swallows. Any risk of them being carriers is overset by them eating the mosquitos (and those annoying horse flies).
Always use insect repellant on both yourself and your horse when riding in summer. You may also want to spray horses before turnout or soak rugs in insecticide or repellent. If you would rather not use DDT-based sprays on your horse, there are a number of natural repellents available.