There are few areas where West Nile virus is not a problem for people and horses alike. Although humans and horses can both get the disease, it can only be transmitted from one animal or human to another through the bite of the mosquito. There is no record of anyone every getting West Nile virus from a horse nor of an uninfected horse getting West Nile from contact with an infected horse.
The mosquito becomes infected with the disease by biting a bird that has West Nile virus. The virus then moves to the mosquito's salivary glands and multiplies but does not kill the mosquito, making it a carrier. The mosquito then bites the horse and the horse becomes infected. Any horse can become infected with West Nile if it is bitten by an infected mosquito. There are currently vaccinations that are being used to prevent the severity of the West Nile virus, although how effective they are is not yet fully understood.
West Nile virus results in symptoms that include loss of appetite, weakness, fever, staggering and lack of coordination, trouble swallowing, pressing the head against objects, muscle seizures and twitching, wandering in circles, hypersensitivity to light, sound and movement and collapse, coma and death in extreme cases. Most horses with West Nile will recover with treatment, but without supportive types of treatments they are more likely to die.
Once a horse has West Nile virus all that can be provided is supportive care. Vets can treat for any secondary bacterial infections and horses can be given anti-inflammatories and pain medications to ease discomfort. Highly palatable feeds with supplements should be provided if the horse is eating at all. Keeping the horse in a warm, dry area that is free from sudden sounds, light or movement will help with the hypersensitivity problem. Lots of fresh, clean water should always be available.
The key to preventing West Nile virus in your horse or horses is to vaccinate for the virus as well as control mosquito populations in your horse's environment. Remove all standing water on the property, especially around the stable or pasture. Use a good quality fly and mosquito repellent routinely both on the horses and in the stable area. Fogging or treating the stables with safe insecticides, especially in the dawn and dust times when mosquitoes are most active will help.
Keep informed as to any cases of West Nile virus in your area. If you are aware that there has been a case or if there are cases in neighboring areas or counties be sure to have your horses vaccinated. Avoid riding or trailering your horse through locations where there have been current reported cases of West Nile virus. Lastly, watch for any signs of dead birds, particularly crows and jays and immediately call the health department if the cause of death of the bird is not evident. Testing can then be done on the dead bird to see if they had the virus.