EHV-1, EHM, and the Questions Horse Owners Are Still Asking
Your Horse Already Has This Virus
Last year, EHV-1 dominated conversations across the horse world.
Horses were hospitalized. Some were euthanized. Competition schedules were questioned. Owners refreshed social media feeds looking for updates from Texas, Las Vegas, and every major western circuit stop connected to the outbreak.
Then the conversation faded.
The virus never left.
That may be the most important point in this conversation on The NOËLLE FLOYD Podcast with equine internal medicine specialist Dr. Bruno Karam.
Most horse owners think about EHV-1 as something that arrives during an outbreak. A threat that appears, spreads, and eventually disappears. The reality is far less dramatic and far more complicated.
Almost every horse has already been exposed to EHV-1. Most carry the virus for life. A horse can acquire it at a young age, recover from the initial infection, and continue carrying it for years. During periods of stress, illness, travel, or for reasons that remain poorly understood, the virus can begin shedding again.
A horse can look healthy while participating in that cycle.
That reality changes the way we think about disease outbreaks. An outbreak is rarely the arrival of something new. It is often the point where something that has been present all along becomes impossible to ignore.
Part of the challenge is that EHV-1 and the neurological disease associated with it often get blended into a single conversation.
They are related, but they are not the same thing.
EHV-1 is the virus. EHM, Equine Herpes Myeloencephalopathy, is the neurological disease that can develop following infection.
Most horses exposed to EHV-1 never experience that outcome. Many encounter the virus early in life and move on with little fanfare. The neurological cases are the ones that command attention because the consequences are so severe.
The videos circulating during last year's outbreak were difficult to watch. Horses struggled to coordinate their limbs. Some became unable to stand. Those images shaped public perception of the disease, yet they represent only one possible outcome from a virus that exists far more broadly than many horse owners realize.
That raises an obvious question.
If so many horses carry EHV-1, why do some develop severe disease while others never show signs at all?
Dr. Karam returns to a principle familiar across medicine. Disease is a conversation between the pathogen and the individual. Two horses can encounter the same virus and have entirely different outcomes. Researchers continue studying the factors that influence those responses because the answer remains incomplete.
Last year's outbreak highlighted another reality. Modern horses travel in ways that create ideal conditions for contagious disease.
Large competitions bring together horses from many regions. They travel long distances. They arrive in unfamiliar environments. They share facilities with hundreds of other horses. The stress of travel and competition creates opportunities for viruses to move through a population with remarkable efficiency.
The concern surrounding the western circuit reached such a high level because of how frequently those horses move. A horse can leave one venue, travel to another, and arrive before showing clinical signs. By the time illness becomes apparent, exposure may have already extended across multiple states.
Those circumstances place an enormous responsibility on horse owners, trainers, veterinarians, and event organizers.
They also explain why Dr. Karam keeps returning to one surprisingly simple tool: a thermometer.
Among all the diagnostics available to modern veterinary medicine, temperature monitoring remains one of the most valuable habits a horse owner can develop. A horse's normal temperature range tells a story. Subtle changes often appear before more obvious clinical signs.
The goal is not panic, but awareness.
That same philosophy applies to vaccination. One of the most common criticisms surrounding EHV vaccination is that current vaccines target respiratory disease and offer limited protection against the neurological form. Dr. Karam's perspective centers on risk reduction. Vaccinated horses may experience milder disease and may shed less virus, reducing opportunities for transmission throughout a population.
Medicine rarely deals in absolutes. Veterinary medicine certainly does not.
Throughout the conversation, Dr. Karam returned to an idea that extends well beyond EHV-1. Science continues moving forward because every outbreak, every study, and every case contributes another piece to the puzzle. The recommendations we follow today are informed by the knowledge available today. Future outbreaks will bring new questions and new data.
For horse owners, that means staying curious, staying informed, and paying attention before the headlines arrive.
Because the next outbreak will begin long before anyone starts talking about it.
