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April 21, 2023

Equine Herpes Myeloencephalopathy Confirmed in Horse at Tulsa County Show

OKLAHOMA CITY – The Oklahoma Department of Agriculture, Food and Forestry has confirmed a case of Equine Herpes Myeloencephalopathy (EHM), the neurologic disease linked to Equine Herpes Virus (EHV-1), in a horse that was present at the National Reining Breeders Classic in Tulsa County on Thursday, April 20, 2023.

The horse showed signs of ataxia and other neurologic signs consistent with EHM when evaluated by a veterinarian. Since EHV-1 is contagious, horses determined to have direct, known exposure with the positive horse were moved to an area of isolation and testing is ongoing.

ODAFF State Veterinarian Dr. Rod Hall has asked NRBC participants to monitor horses for clinical symptoms of illness or fever while a complete investigation is being conducted.

“It is recommended that a horse’s temperature be taken twice daily,” Hall said. “Any temperature over 101 degrees should be reported to the show veterinarian.”

ODAFF staff has been in contact with NRBC and Expo Square management to ensure additional measures of biosecurity precautions have been implemented. Precautions include maintaining at least 30 feet separation from horses in warm up arenas, using the same routes to and from wash racks, competition arenas, and warm up areas, and distributing information sheets to help equine owners understand the causes and ways to prevent EHV-1.

EHV-1 is spread from horse to horse through contact with nasal discharge or spread as aerosol droplets. Distance between horses should be maintained whenever possible. Sharing of grooming and feeding equipment is discouraged because EHV-1 can also be spread on tack, clothing, and other equipment.

For more information about EHV-1, including symptoms and treatment, visit