Minnesota officials have confirmed via post-mortem testing that a 6-week-old Quarter Horse euthanized in Clay County on July 15 was infected with the highly contagious disease equine herpesvirus-1 myeloencephalopathy (EHM). The Minnesota Board of Animal Health is responding to the case by activating its EHM control plan and placing the Clay County farm under quarantine to closely monitor the rest of the resident horses for EHM.

On July 15 the examining veterinarian observed the foal had worsening neurologic signs: His lower lip was hanging loosely, he was biting at his front legs, stumbling, and circling, and he was unable to rise on his own. This led to the decision to euthanize the animal. The University of North Dakota Veterinary Diagnostic Laboratory performed a necropsy on the horse, confirming EHV-1 infection based on the foal’s clinical neurologic signs and positive EHV-1 test results.

“This case is a good reminder that despite the fact we’ve had no reported EHM cases in Minnesota since 2015, it still poses a significant risk to horses,” said Courtney Wheeler, DVM, Minnesota Board of Animal Health’s Equine Program director. “Horse owners should take this opportunity to review their biosecurity protocols, both on the farm and when traveling, to ensure they are doing their best to protect their horses and Minnesota’s equine community from communicable and contagious diseases like EHM.”

The most common way for EHM to spread among horses is by nose-to-nose contact. It can also spread via contact with contaminated objects such as tack, feed and water buckets, grooming equipment, and a person’s clothing (a person handling an infected horse can also transfer the virus on their hands). Horses might appear healthy yet still spread the virus