California Confirms Fourth Equine WNV Case of 2012

The California Department of Food and Agriculture (CDFA) confirmed one additional case of equine West Nile virus (WNV) on Friday (Aug. 3), according to a statement on the organization's website.

"On August 3, 2012, the CDFA Animal Health Branch confirmed one additional case of West Nile virus in a 3-year-old unvaccinated filly in Fresno County," the statement read. "The filly is recovering."

The Fresno County filly is the fourth California horse to test positive for WNV in 2012. The three other positive cases were identified in Glenn, San Joaquin, and Stanislaus counties. Only one of the four horses has been euthanized to date.

In a blog post published July 31, California State Veterinarian Annette Whiteford, DVM, said, "Each year, we find ourselves using this sad occasion to remind horse owners to have their animals vaccinated. It offers them maximum protection against the disease. And once vaccinations occur, horse owners should be checking regularly with their veterinarians to make sure they stay current."

Clinical signs for WNV include flu-like signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

The USDA Animal and Plant Health Inspection Service reported 83 cases of WNV in U.S. horses in 2011, with 15 of those cases being identified in California horses.

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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