Progression of the Ohio EHV-1 Outbreak

There were 138 horses stabled at the University of Findlay James L. Child Jr. Equestrian Complex when the equine herpesvirus type 1 (EHV-1) outbreak hit. Beginning Jan. 12, many horses began showing non-specific symptoms, including fever and depression. Some horses also exhibited mild nasal discharge and would not eat. Within 48-72 hours, approximately 85% of the horses showed similar signs.

Over the weekend of Jan. 18, neurologic signs surfaced in many of the horses, and the virus was suspected to be EHV-1. The virus was confirmed to be EHV-1 on Jan. 24 through tests completed with the Ohio Department of Agriculture and The Ohio State University (see article #4084).

Rick Henninger, DVM, a veterinarian at the University of Findlay, treated horses in the outbreak. "No horse necessarily went by the book," he said. The horses typically developed fevers, followed by mild nasal discharge, and the worst ones developed neurologic signs. "Typically they'd have a fever for four to seven days," he said. "If the horses developed neurologic symptoms, they'd usually start on day six, seven, or eight.

"Why did we have some horses that never suffered at all?" asked Henninger. "It was not a large percent, but there were some. We have some horses that got fevers and then did not develop (further symptoms)."

Henninger explained that the disease manifested itself in different ways in different horses, much like a cold or flu spread to a room of people might give different people different clinical signs, and might not even affect some individuals.

"It probably has something to do with their immune status related to their vaccination history, age, stress, and other things just like with people," he said. All of those factors play a part in the morbidity of a virus, and also you have to factor in the virulence of the virus."

"It very well may be that every horse was exposed, and some infections were so mild that we didn't ever recognize any symptoms in those horses," he said.


Neurologic horses received anti-inflammatory drugs and Banamine (flunixin meglumine) or pain reliever. They also received IV fluids containing DMSO and acyclovir, a human herpes drug. Most of the other (mildly affected and even asymptomatic) horses received acyclovir orally as a paste to try and fend off more severe symptoms. Henninger said that any horse with moderate to severe neurologic signs was moved to the English riding facility's large arena for anti-viral, anti-inflammatory, and supportive treatment. "If they were going to become recumbent, we didn't want them to be in a stall. It was like triage-we could keep a better eye on them, and share the help."

Four horses were sent to The Ohio State University when they became too weak and ataxic for supportive care at Findlay. Some of those horses were put in Andersen Slings to support them and to aid in their recovery. (See article #44 on slings).

As neurologic horses being treated at the University of Findlay stabilized, they went back to their stalls, he said. As of Feb. 4, he said with relief. "There are none in the arena now."

Henninger explained that a few of the sick horses seemed to regress slightly, and there are ongoing issues related to the horses' clinical signs. "Even though their neurologic status is stable, some are incontinent and catheterized," he said. Whichever part of the spinal cord was affected controls the problems they are experiencing. "Those are improving," he said, "it just prolongs the care, and some are still mildly incoordinated."

For the horses which weren't affected neurologically, but had fevers and respiratory signs, "Some are quiet and mildly lethargic, but exhibit nothing specific (in terms of clinical signs) other than they are not quite back to their normal selves," he said.

The University of Findlay's veterinarians continue to consult with The Ohio State University veterinarians and other experts and agencies in order to provide the best possible care to the horses and prevent spread to other horse populations. Henninger and officials will not consider the outbreak finished until significant time has passed since the last report of fevers. "We haven't gone two weeks without fevers yet," he explained.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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