The power of preparedness against equine herpesvirus
A horse with a runny nose or mild cough may not immediately raise alarm, but what happens when signs of minor respiratory illness have potential to become something much more serious?
During last year’s Equine herpesvirus, EHV, outbreak, the equine community saw this scene occur right before their eyes. Initially appearing to be a mild case at a barrel race in Waco, Texas, rapidly spread into more than 50 reported infections.
From the time of the event on November 5, 2025 to January 1, 2026, the Texas A&M Veterinary Medical Diagnostic Laboratory, TVMDL, performed 757 tests for EHV-1 and 4.
Equine veterinarian and veterinary diagnostician for TVMDL, Semira Mancill, DVM, DACT, said that she couldn’t be more proud of how well the laboratory team worked in the midst of the outbreak.
“In the best way, our lab worked together to serve our equine practitioners, Texas animal health, and equine owners at a time when emotions and stress was at its absolute limit,” Mancill said.
One virus family with multiple types
Equine herpesvirus, or EHV, includes nine reported types of viruses that can affect horses. TVMDL, offers testing for EHV types 1, 2, 4, and, 5, giving veterinarians access to valuable diagnostic insight when EHV is suspected.
Of those, EHV-1 often draws the greatest concern because of the range and severity of disease it can cause.
EHV-1 can present in several ways. Some horses may show no obvious clinical signs, while others develop fever, nasal discharge, coughing, sneezing, decreased appetite, or general lethargy. The virus can also cause abortion and disease in newborn foals.
“Typically when we see abortions from EHV-1, it’s going to be late-term abortions,” Mancill said. “It can be anytime during gestation, but it occurs more commonly in late term.”
Among the virus’s most serious manifestations is equine herpesvirus myeloencephalopathy, or EHM.
“The neurologic form is the one that is typically fatal,” she said. “If they just get the respiratory form, it’s usually self-limiting. They get sick for a little bit and then they get over it, just like a cold or maybe a mild flu. But EHM is the one to really watch out for.”
Signs associated with EHM may include incoordination, weakness, difficulty standing, or even head tilt.
“The signs start showing in the rear legs, so horses will often get ataxic in the hind end,” Mancill said. “Some of them will dog sit, and they might have trouble urinating.”
Diagnosing EHV
The wide range of possible clinical signs is one reason why diagnostic testing is important. Signs of mild respiratory disease can resemble several other infections, and appearance alone may not always tell the full story.
At TVMDL, EHV-1 testing is offered alongside EHV-4 through EHV-1/EHV-4 PCR and virus neutralization testing. TVMDL also recently added EHV-2 and EHV-5 to respiratory testing panels.
Advantageously, the laboratory has the capability to further characterize EHV-1-positive samples for the genetic marker associated with the neuropathogenic form of the virus.
These diagnostic capabilities became particularly valuable during the major EHV-1 outbreak in late 2025.
“If you’re seeing respiratory signs and not sure what it could be, our respiratory panels, especially the comprehensive panel, would be a great place to start with your diagnostics,” Mancill said.
Reducing the risk of EHV
Although outbreaks of the magnitude seen in 2025 are uncommon, environments that bring many horses into close contact can create opportunities for disease to spread.
Horses at shows, rodeos, and other events may frequently be in close proximity and encounter shared surfaces, equipment, people, and other horses.
“One hundred percent, biosecurity is, hands down, the best way to prevent diseases being passed from animal to animal,” Mancill said. “Just a few ways to practice prevention include not sharing tack, bring your own water buckets, and if there’s open stall walls, bring covers to cover those openings so that nobody can be nose to nose.”
When questions do arise, veterinarians do not have to navigate them alone. If owners and veterinarians see that something might be wrong, TVMDL is just one call away.
Preparedness powered by people
TVMDL is well prepared with advanced instrumentation and testing capacity to handle a highly contagious, rapidly spreading, viral event, but it’s the dedicated people running the tests that make efficiency possible.
As veterinarians and horse owners were in the midst of the 2025 EHV-1 outbreak, TVMDL employees gladly responded with extended hours, weekend work, and expedited testing.
“It was great, the way our team came together,” Mancill said. “Our experts are highly prepared to take in large numbers of samples, run those samples in a very efficient manner, and to get validated, accurate results back fast.”
TVMDL has the drive and devotion, and it’s always ready to act against disease in the name of animal health.
For information about veterinary diseases or TVMDL’s test offerings, visit tvmdl.tamu.edu or call the College Station laboratory at 888-646-5623.
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