EHM in Wyoming: Case Diagnosed in Johnson County

The affected 15-year-old Quarter Horse mare is quarantined at her home facility in Johnson County along with 19 other horses.

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ehm in wyoming
In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. | Photo: Alexandra Beckstett/The Horse
The Wyoming Livestock Board (WLSB) announced April 5 that veterinarians have diagnosed a horse in Johnson County with equine herpes myeloencephalopathy (EHM), the neurologic form of equine herpesvirus-1 (EHV-1).

The Equine Disease Communication Center said the affected 15-year-old Quarter Horse mare, which had been vaccinated, began showing neurologic signs, including hind-end weakness, on April 3 and was confirmed positive for EMH on April 4. The WLSB said the mare is quarantined at her home facility in Johnson County along with 19 other horses.

It is currently unknown where the horse contracted the disease, but she attended college rodeo events March 15-16, at the Camplex in Gillette, Wyoming, and March 21-24 at the Goshen County Fairgrounds, in Torrington, Wyoming.

Thach Winslow, DVM, Wyoming assistant state veterinarian for field operations, said any horses that were at these events should be considered potentially exposed, and owners should take preventive measures, including monitoring the animals closely and checking their temperatures at least twice daily. If any horses show neurologic signs or fever, owners should isolate them and contact their veterinarians for advice and treatment options

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