West Nile Virus In Horses
   Diagnosis and Prevention Tips

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Diagnosis of WNV in Horses
Diagnosis of WNV infection in horses involves testing the blood serum for antibodies against the virus. Horses vaccinated for WNV and foals of positive-testing mares are likely to have a positive blood test for the virus. Veterinarians consider blood test results, clinical symptoms and the possibility of other neurological diseases, including rabies, Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), Equine Rhinopneumonitis (equine herpes virus type 1), and Equine Protozoal Myeloencephalitis (EPM), before making a diagnosis. Blood samples should be collected by a veterinarian and sent to the National Veterinary Services Laboratory. Because of the potential for rabies and the related risk to humans and animals, the heads of horses that die or are euthanized due to neurological disease should be submitted for testing to National Veterinary Services Laboratory.

Treatment and Long-term Effects of WNV
Currently, there is no specific treatment for the disease caused by WNV. Supportive therapy should be administered by the horse owner's veterinarian to reduce clinical signs and the possibility for secondary infections. When a horse becomes infected, with or without clinical disease, that horse develops antibodies in response to the infection. Infected horses can acquire long lasting immunity to WNV after recovery, due to these antibodies. If the horse develops encephalitis, there may not be full recovery and the horse may possibly have permanent central nervous system damage.

Protecting Your Horse from WNV
Vaccine is available as an aid in control of WNV in horses. The vaccine is safe and has been shown to provide protection in horses. The WNV vaccine is similar to vaccines against EEE and WEE and is only available through licensed veterinarians. Horses vaccinated against EEE, WEE, and Venezuelan Equine Encephalitis are not protected against infection with WNV. Horse owners are advised to consult their veterinarian concerning WNV vaccination of their horses. Vaccinated horses can be differentiated from infected horses on laboratory tests. In addition to the vaccine for horses, simple insect control measures should be utilized. Consider the use of insect repellents, and place horses under fans in barns/stables at dusk, dawn, and other times when mosquitoes are present. Eliminate opportunities for mosquito breeding by draining wet areas of pasture, filling puddles, repairing eaves troughs, gutters, etc.; clearing any containers that might hold even small pools of water; and draining water tanks once or twice weekly. Additionally, consider control of mosquitoes in ponds and large water containers through the use of larvacides and fish.