On Sept. 13 the Ohio Department of Agriculture confirmed the first positive cases of West Nile virus (WNV) in Ohio horses for 2017. Multiple cases in different parts of the state have been reported. None of the horses confirmed to have contracted WNV had been vaccinated.

The spread of WNV in horses is preventable with proper vaccination and horse owners are urged to ensure their animal’s vaccinations and boosters are up-to-date.

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%.

The WNV cases follow the Ohio Department of Agriculture’s report of Eastern equine encephalitis (EEE) in an Ashtabula County horse on Aug. 24. That horse was unvaccinated against EEE