EHV spreading through horse populations— What you should know

Biosecurity is always on the minds of farmers and ranchers as they work to keep their livestock healthy, especially in a time where one disease outbreak after another seems to be threatening their animals.  In the news we continue to hear concerns of avian influenza, Foot-and-Mouth Disease, and African Swine Fever affecting farms and ranches across the US.  Now adding to the list is the equine herpesvirus (EHV), a well known disease that has unfortunately ramped up and began to spread throughout the country.

The recent outbreak has been traced back to the Women’s Professional Rodeo Association (WPRA) World Finals and Elite Barrel Racing event in Waco, Texas, held November 5-9.  Horses infected with the highly aggressive and contagious disease then carried it to several states, including Oklahoma, Louisiana, Colorado, and New Mexico where positive cases have been confirmed.

EHV is not a new disease infecting horses, but the current outbreak is very disconcerting and creating huge ripples in the horse community from national events to just everyday transport and use.  EHV commonly causes fever and upper respiratory signs, but in some horses, the disease progresses to Equine Herpes Myeloencephalopathy (EHM), a neurological form of the disease.  

The Equine Disease Communication Center (EDCC) states that EHV-1 will cause neurologic signs as a result of inflammation of the blood vessels and activation of blood coagulation within the brain and spinal cord. Neurologic signs occur as a result of a lack of blood flow and resulting damage to the brain or spinal cord, full progression to this state being classified as EHM. 

Classic clinical signs of EHM include fever, swelling/stocking up of the limbs, hindlimb weakness, and urine dribbling. Some horses are more severely affected and display behavior changes, signs of cranial nerve dysfunction, seizures, and inability to stand. While EHM is a serious disease, the majority of cases are not fatal. In most outbreaks of EHM, 60-70% of affected horses recover with treatment and supportive care.

The first signs of infection include fever, nasal discharge, hindlimb weakness or stumbling, difficulty urinating or defecating, loss of tail tone (“dead tail”), dog-sitting posture and a drunken or wobbly gait.  

Like so many viruses, EHV is spread through the nasal discharge of horses.  Those infected droplets then land on surfaces that horses will lick or chew on, internalizing the disease.  Shared water buckets, bits, lead ropes, feed, salt blocks, barn stalls, and even people can serve as a vector to spread the disease. 

The seriousness of the disease, its affects, and the spread have led to a number of guidelines and restrictions for horses in the coming weeks and months.  Horses that have been to an event with a confirmed case of EHV are required to quarantine for 21 days.  Infected horses are to be isolated for at least 14 days after a positive test of EHV.  

Reducing the spread of the disease has been the number one priority, beginning with the cancellation and postponement of multiple events.  Unfortunately, this time of year features a number of national events that are having to disrupt their upcoming schedules or risk further spread of the disease.  

The San Antonio Rodeo qualifier, scheduled to be held in Uvalde, Texas, the Prairie Circuit Finals, in Mulvane, Kansas, and the Barrel Futurities of the America World Championship in Guthrie, Oklahoma have all been canceled.  

The OKC Futurity planned for December 9-14 in Oklahoma City is being highly monitored with potential schedule changes.  Similarly, the NRHA Futurity, held through the end  November until December 6 in Oklahoma City, will proceed as planned while monitoring the situation, since no confirmed cases have been purported at the venue. 

The National Finals Breakaway Roping (NFBR) has officially been postponed, as well as the PRCA Permit Finals.  The National Final Rodeo (NFR) is still set to be held as scheduled, but with further restrictions and requirements, unless a positive case is found.

Understandably, there has been a bit of panic circulating in the horse world.  Instead of panicking, people should feel confident that veterinarians have a good handle on the epidemiology of EHV, how outbreaks happen, and how to handle the aftermath. The truth is that very few horses die from this disease.  The last outbreak in 2011 found only a small percentage of horses passing from the disease and even fewer with lasting effects.  Simple, smart, common sense actions will go a long way to keep horses safe and healthy, the goal of everyone in the horse world.