West Nile virus confirmed in Ohio horses

Diseases spread by mosquitoes are preventable in horses with proper vaccination.

REYNOLDSBURG, Ohio — The Ohio Department of Agriculture confirmed the first two positive cases this year of West Nile virus in Ohio horses.

A horse in Stark County confirmed with West Nile virus was vaccinated once in the spring but did not receive a booster. The second horse’s county of origin and vaccination history are not yet known.

The spread of West Nile virus in horses is preventable with proper vaccination and horse owners are urged to ensure their animal’s vaccine and boosters are up to date. West Nile virus is transmitted to horses via bites from infected mosquitoes.


Clinical signs for West Nile virus include flulike symptoms, where the horse seems mildly anorexic and depressed. Changes in mentality, drowsiness, driving or pushing forward (often without control), and asymmetrical weakness may be observed.

The mortality rate from West Nile virus can be as high as 30-40% in horses. Infection with West Nile virus does not always lead to signs of illness in people or animals.

West Nile virus is endemic in the United States and Ohio has reported positive cases in horses each of the last few years.

Eastern equine encephalitis

These West Nile virus cases follow the Ohio Department of Agriculture’s report of Eastern equine encephalitis in an Ashtabula County horse Aug. 29. Since then, two additional horses have been confirmed with eastern equine encephalitis, one each in Geauga and Portage counties.

“West Nile Virus and eastern equine encephalitis are serious diseases that can be prevented with proper vaccination,” said State Veterinarian Dr. Tony Forshey. “I encourage all owners to work with their local vet to keep their animals healthy.”

In addition to vaccinations, horse owners also should work to reduce the mosquito population and eliminate possible breeding areas.

Recommendations include: removing stagnant water sources; keeping animals inside during the bugs’ feeding times, which are typically early in the morning and evening; and using mosquito repellents.


Because West Nile virus and eastern equine encephalitis can also be transmitted to humans by the bite of infected mosquitoes, animals diagnosed with these diseases are a sign that people should also take steps to guard themselves against mosquitoes by applying repellent and wearing protective clothing.

Both diseases are very rare in humans, and only a few cases are reported in the United States each year. There are no confirmed human cases associated with any of these equine cases in Ohio.

The Ohio Department of Agriculture is working with the Ohio Department of Health and local health officials to monitor both outbreaks. Suspect horse cases should be reported to a veterinarian as soon as possible. Citizens who are concerned about an illness should contact their physician.


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