Neurologic EHV-1 Confirmed in Minnesota Foal
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.

It is crucial that horse owners adhere to stringent biosecurity practices to prevent the further spread of EHM and other contagious equine diseases. A general biosecurity steps flyer is available on the board’s website.

Veterinarians continue to identify multiple EHM cases throughout the United States. Due to the highly contagious nature of this disease, all cases of EHM in Minnesota must be reported to the state’s animal health board which, in collaboration with Minnesota’s equine industry, enforces an official control plan for EHM. Under the plan, the board is required to quarantine, test, and monitor all horses confirmed to have, or been exposed to, EHM. You can review the EHM control plan on the board’s website.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and EHM.

In many horses, the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but can be earlier. Abortions can occur anytime from two weeks to several months following EHV-1 infection.

Horses with the neurologic form usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should always be in place to help present disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.