Department Confirms Two Unrelated Cases of Equine Herpesvirus Myeloencephalopathy in Anne Arundel, Cecil Counties (UPDATED 3/19/21)

ANNAPOLIS, MD – The Maryland Department of Agriculture (MDA) Animal Health Program has confirmed two unrelated cases of Equine Herpesvirus Myeloencephalopathy (EHM). Both horses developed clinical symptoms over the weekend, and were confirmed positive for EHM on Monday, March 8. The horses were stabled in different counties (Anne Arundel, Cecil) and there is no known connection between the horses.

A horse stabled at Laurel Park Racetrack in Anne Arundel County began displaying clinical symptoms of EHM on Saturday, March 6. The symptomatic horse was sent to Marion duPont Scott Equine Medical Center in Leesburg, Va., where the wild-type strain of Equine Herpesvirus (EHV-1) was confirmed, this is the virus that causes EHM. The horse remains at the medical center and is responding well to treatment.

MDA has placed four barns at Laurel Racetrack on a hold order, prohibiting movement on or off the premises until any exposed horses have been cleared for release. The hold order is a precaution for any horses that were potentially exposed to the positive horse. No other horses are showing clinical signs at this time. Horses under the hold order will be closely monitored for any clinical signs, and any horses showing clinical signs will be tested immediately. MDA Animal Health staff is working closely with Laurel Park to ensure that their daily operations are able continue as safely as possible.

A second unrelated horse stabled at a private barn in Cecil County began displaying clinical signs of EHM on Friday, March 5. The horse did not respond to treatment and was euthanized on Saturday, March 6. Samples from the deceased horse were confirmed positive for EHM on Monday, March 8. The barn has been placed on a hold order, with veterinary professionals monitoring all horses for clinical signs. The hold order will remain in place until all exposed horses have been cleared for release. 

Owners are cautioned to monitor horses at their premises carefully, and should contact their private veterinarians to arrange for Equine Herpesvirus testing if a horse exhibits significant temperature elevations or neurologic signs. Veterinarians are required to report equine neurologic syndrome to the department by calling the Animal Health Program at (410) 841-5810.

**UPDATE (3/19/21)**

MDA has confirmed additional cases of EHV-1 at Laurel Park Racetrack. A second horse in the same barn as the index horse began displaying clinical signs of EHV-1 and was confirmed positive on March 15. That horse did not respond to treatment and has been euthanized.

Following the second positive case, MDA Animal Health officials tested the remaining 20 horses housed in the same barn as the two positive horses on March 17. Those tests returned six positive results from asymptomatic horses. All positive horses have been removed from the barn and placed in isolated quarantine offsite. The original hold order on the four impacted barns has been reset, and horses in the index barn will be retested prior to releasing the order. The department continues to work closely with Laurel Park Racetrack and Maryland Jockey Club to ensure that daily operations are able to continue as safely as possible with minimal disruption.

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