EHM in Sheridan County, Wyoming, Horse
A horse in Sheridan County, Wyoming, has tested positive for neurologic herpesvirus.

A horse with neurologic herpesvirus was confirmed in Sheridan County, Wyoming. Google maps

The Wyoming Livestock Board confirmed that a horse in Sheridan County has tested positive for equine herpesvirus myeloencephalopathy (EHM). The horse has been quarantined at its premise in Sheridan County with 12 other horses. 

The affected horse began showing neurologic signs on Sunday, March 11, while competing at a barrel racing event at the Cam-plex facility in Gillette. Owners of any horses attending that event should consult with their veterinarians and take precautions regarding exposure risk. 

At a minimum, these precautions should include close monitoring of the horses and checking their temperatures at least twice daily. 

If any of the horses show neurologic signs or fever, the owner needs to contact his/her veterinarian and the Wyoming Livestock Board. 

Although the source of the infection in the quarantined horse is unknown, this horse did compete at the Central Wyoming Fairgrounds in Casper on Thursday, March 1, and at Laramie County Community College, Friday, March 2 – Sunday, March 4. 

Horses at the events might have been exposed. 

Because the incubation period for the disease is less than 14 days, clinical signs should have been apparent in any exposed horses. However potentially exposed horses should be monitored for at least 14 days since any possible exposure at events. 

More information on equine herpesvirus can be obtained by contacting the Wyoming Livestock Board Field Office at 307-857-4140 or by going to and


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