The California Department of Food and Agriculture (CDFA) reported July 13 the state’s first confirmed equine West Nile virus (WNV) case of 2017.

“On July 13, 2017, a 14-month-old Quarter Horse filly in Kern County, displaying severe neurologic signs, was confirmed positive for West Nile virus (WNV),” the agency said in a statement. “Due to the severity of signs, the filly was euthanized.

“CDFA continually monitors and investigates equine neurologic cases for the presence of WNV in California,” the statement continued. “CDFA urges horse owners to consult their veterinarian concerning a WNV vaccination program to ensure maximum protection of their horses.”

West Nile is transmitted to horses via bites from infected mosquitoes. Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculation; 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. Equine mortality rate can be as high as 30-40%