The return of West Nile virus to California this year is renewing calls for horse owners to make sure their animals are vaccinated. So far in 2010, four horses have been diagnosed with the disease, in Sacramento, San Joaquin and Madera counties. All of the horses were either unvaccinated or incompletely vaccinated.

“Outbreaks of West Nile virus are still a risk for horses,” said California State Veterinarian Dr. Richard Breitmeyer. “Horse owners should contact their veterinarians as soon as possible to ensure vaccination status is current. If people get the necessary shots for their horses now, the animals will have optimal protection against the disease.”

Signs of West Nile virus include stumbling, staggering, wobbling, weakness, muscle twitching and inability to stand. Horses contract the disease from carrier mosquitoes and are not contagious to other horses or people. Not every horse exposed to the virus will die.

CDFA is cooperating with the California Department of Public Health to detect and respond to the disease in California. Horses provide an additional sentinel for disease detection.