First horse in Virginia tests positive for West Nile Virus

Posted at 1:28 PM, Sep 28, 2012
and last updated 2012-09-28 13:28:24-04

The Virginia Department of Agriculture and Consumer Services today announced 2012’s first positive case of West Nile Virus in a horse. The horse, a nine-year-old Morgan gelding, was from Loudoun County and had not been vaccinated for West Nile for at least three years.

The horse was euthanized and necropsied at VDACS’s animal health laboratory in Warrenton on September 13.

Dr. Joe Garvin, head of VDACS’ Office of Laboratory Services, urges horse owners to check with their veterinarians about vaccinating their animals for West Nile. “West Nile is a mosquito-borne disease,” he said, “and we generally start seeing our first cases in August and September. The disease is preventable by vaccination, as is Eastern Equine Encephalitis, so many veterinarians recommend vaccination at least yearly, and in mosquito-prone areas, every six months.” He adds that mosquito season in Virginia can run through November.

The vaccine for equines initially requires two doses administered three to six weeks apart. The vaccine takes four to six weeks from the second dose for optimal effectiveness. Horse owners should consult with their veterinarians to choose a re-vaccination schedule to protect their horses effectively.Prevention methods besides vaccination include destroying standing water breeding sites for mosquitoes, use of insect repellents and removing animals from mosquito-infested areas during peak biting times, usually dusk to dawn.

Mosquitoes can transmit the virus from bird to bird. Occasionally a mosquito that has bitten an infected bird will then bite a human, horse or other mammal and transmit the virus to them. Transmission between horses and humans is extremely unlikely. Continuous, effective mosquito control can minimize the risk of exposure of both horses and humans to mosquito-borne diseases.

Currently, no drugs exist to treat West Nile specifically in horses or humans.

Animal owners should consult their veterinarians if an animal exhibits any neurological symptoms such as a stumbling gait, going down, facial paralysis, drooping or disinterest in their surroundings. Currently, there are live-animal tests for West Nile in horses and chickens, but none for other animals, although testing can be done on any dead animal.

Animal owners should consult their veterinarians or the nearest VDACS Regional Animal Health Laboratory for advice or information should an animal exhibit symptoms of WNV. The location and phone number of each lab is available at