SPARKS, Nev. — With mosquito season just around the corner, the Nevada Department of Agriculture is advising all horse owners to contact their veterinarians and update their animals’ West Nile Virus (WNV) vaccinations.

WNV is transmitted by mosquitoes, which are active in warm seasons. Since 2004, there have been 205 confirmed cases in Nevada of WNV in horses.

WNV causes encephalitis in horses, resulting in loss of appetite, depression, fever, lack of coordination, hind limb weakness, muscle twitching, convulsions and the inability to swallow. Approximately one-third of unvaccinated horses, which contract the disease, dies or must be euthanized

“The vaccine is very effective in preventing disease,” said Dr. Michael Greenlee, Nevada’s state veterinarian. “We encourage horse owners to vaccinate their animals to ensure their health and well-being.”

In addition to vaccination, equine owners can take other measures to reduce exposure to mosquitoes.

Owners should eliminate potential breeding sites, which include any item that can hold standing water such as old tires and other small containers. They should also keep horses inside during the peak mosquito activity period of dusk to dawn and avoid the use of lights that may attract mosquitoes. Use of EPA approved repellents will provide another layer of protection for their animals.

View a video about WNV protection for horses,, or visit for more information.