WNV transmission occurs when infected mosquitoes feed on animals, as well as humans, after having fed on infected birds. | Photo: iStock

California Department of Food and Agriculture (CDFA) officials have confirmed four horses with West Nile virus (WNV) as of Sept. 14.

On Aug. 23, a yearling Quarter Horse gelding in Stanislaus County began showing clinical signs that included mild fever, ataxia (loss of muscle control), and falling over. He had an unknown vaccination status and was confirmed positive on Sept. 3. He is affected and alive.

That day, a 3-year-old Buckskin gelding in San Bernardino County began experiencing ataxia. He was confirmed positive on Sept. 10 and is affected and alive. His vaccination status is unknown