The Virginia Department of Agriculture and Consumer Services (VDACS) announced July 10 the state’s first positive case of West Nile virus (WNV) in a horse in 2017. It is the first case since August 2015 in Virginia.

The affected horse, an unvaccinated 10-year-old Saddlebred gelding from Wythe County, exhibited loss of control of bodily movements, partial paralysis in the hind limbs, a dazed appearance, and eventually became unable to stand. The horse was euthanized due to the severity of his clinical signs.

The horse was necropsied at VDACS’ Regional Animal Health Laboratory (RAHL) in Wytheville and tested positive on June 29 at the Warrenton RAHL via a serologic test. The positive was confirmed at the National Veterinary Service Laboratories on July 7.

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%