By Blake Jackson
An outbreak of equine herpesvirus myeloencephalopathy (EHM) was identified in November 2025 following a Women’s Professional Rodeo Association (WPRA) World Finals and Elite Barrel Race in Texas. Horses from that event later traveled to the Barrel Futurities of America (BFA) World Championship in Oklahoma. Once positive cases were confirmed, BFA promptly cancelled the remainder of its competition.
The primary concern is that many exposed horses left these events before showing symptoms, potentially spreading the virus unknowingly. EHM is caused by equine herpesvirus-1 (EHV-1), and less commonly EHV-4. While these viruses often cause respiratory illness or abortion in mares, certain strains can result in neurologic disease known as EHM.
The virus spreads easily through horse-to-horse contact, airborne droplets, contaminated equipment, and people. Although EHM is serious, the Equine Disease Communication Center (EDCC) reports that approximately 60-70% of affected horses recover with intensive veterinary care.
As of December 8, 2025, 47 neurologic cases connected to these events have been confirmed, along with additional EHV-1-positive horses showing mild or no symptoms. Most cases are located in Texas and Oklahoma, with scattered cases in several other states. No Pennsylvania cases have been linked to this outbreak.
Two separate EHV incidents occurred in Pennsylvania during November 2025 but were unrelated. One involved a respiratory EHV-4 case in Northumberland County, while another outbreak in Lancaster County resulted in three EHM cases, two of which tested positive for EHV-1.
Most Pennsylvania horses remain at low risk. The highest-risk animals are those that attended the affected events or had close contact with those horses. Veterinarians strongly recommend isolating returning horses, monitoring temperatures twice daily, and contacting a veterinarian if symptoms develop.
While vaccines exist for EHV-1 and EHV-4, none are proven to prevent EHM. As a result, strict biosecurity practices such as quarantining new or returning horses, avoiding shared equipment, and limiting contact at events remain the most effective tools to reduce disease spread.
Photo Credit: gettyimages-patrick-jennings
Categories: Pennsylvania, Livestock