The Utah State Veterinarian’s Office has received reports of the first and second cases of West Nile virus (WNV) in horses for 2016, the state Department of Agriculture and Food (DAF) reported Aug. 24.

The first case was in an unvaccinated 4-year-old Quarter Horse gelding from Uintah County. The horse was euthanized because of severe clinical signs. The second horse was also unvaccinated and located in Uintah County.

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 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. Equine mortality rate can be as high as 30-40%.

The Utah DAF said data shows that 80% of cases in horses occur during the months of August and September