A devastating EHV-1 outbreak that began at Texas barrel racing events in early November 2025 has now spread across eight states, with 34 confirmed cases, multiple horse deaths, and hundreds of potentially exposed animals under quarantine. As veterinarians scramble to contain the virus and event organizers cancel competitions nationwide, one message rings clear from every expert: early detection saves lives. The difference between a horse that recovers and one that requires euthanasia often comes down to hours—the critical window between when subtle symptoms first appear and when an owner recognizes the emergency and calls for help.
This comprehensive symptoms checklist arms horse owners with the specific warning signs that demand immediate veterinary intervention. Understanding what to watch for, when fever becomes a crisis, and which neurological symptoms signal life-threatening disease can mean the difference between a contained incident and a barn-wide catastrophe.
Why Early EHV-1 Symptom Recognition Matters More Than Ever
EHV-1 exists as a latent infection in 80-90% of horses by age two, lying dormant in nerve tissue until stress—transport, competition, weather changes, or illness—triggers reactivation. This means apparently healthy horses can suddenly begin shedding infectious virus without warning. By the time obvious illness appears, exposure may have already occurred across an entire barn or event.
The current outbreak exemplifies this pattern. The index event at Waco’s WPRA World Finals brought together approximately 1,000 horses from 31 states and four Canadian provinces. Infected horses returned home appearing normal, then developed fever days later—but had already exposed stablemates during the incubation period. Texas Animal Health Commission officials describe the strain as presenting with “acute progression and high clinical severity,” making rapid recognition even more critical.
Dr. Lynn Martin of the University of Missouri College of Veterinary Medicine emphasizes the stakes: Early indicators like mild fever or nasal discharge might not appear concerning individually, but they can signal EHV exposure. Recognizing these signs early provides veterinarians the best opportunity to intervene and reduce risk to other horses.
Fever and EHV-1: The Single Most Important Early Warning Sign
Before neurological symptoms appear, before respiratory distress becomes obvious, fever announces that something is wrong. For EHV-1, this makes temperature monitoring your most powerful early detection tool.
EHV-1 Fever Threshold: What Temperature Requires Immediate Action
A rectal temperature reaching or exceeding 101.5°F typically signals the first indication of EHV-1 infection. Normal adult equine temperature ranges from 99-101°F. Any reading at or above 101.5°F in a horse that recently traveled, attended events, or had contact with unfamiliar horses warrants immediate veterinary consultation—no exceptions, no “wait and see.”
The fever associated with EHV-1 typically appears 2-10 days after exposure (most commonly 4-6 days) and often precedes neurological signs by 7-12 days. This window creates a crucial opportunity: catch the fever early, isolate the horse immediately, and you may prevent both severe neurological disease in that animal and transmission to others.
Why EHV-1 Fever Patterns Can Deceive Even Experienced Owners
EHV-1 fever patterns don’t always cooperate with owners’ expectations. The fever may spike briefly then drop, meaning a horse checked only once daily could appear normal despite having spiked to 104°F earlier that morning. Some horses show only mild, transient fevers that resolve within 24-48 hours even as the virus continues replicating.
This variability demands twice-daily temperature monitoring during high-risk periods. Check temperatures at consistent times—ideally morning and evening—and log every reading. A pattern of even slightly elevated readings (101.3°F, 101.4°F) that wouldn’t individually trigger alarm may collectively reveal trouble brewing.
Why You Must Not Mask EHV-1 Fever with Bute or Banamine
The temptation to give Bute or Banamine to a horse running a low-grade fever can be overwhelming, especially if the horse otherwise seems comfortable. Resist this impulse absolutely. Do not administer NSAIDs to horses being monitored for EHV-1 unless specifically directed by a veterinarian—these medications mask fever and can delay critical detection by hours or days. That delay can mean the difference between catching disease early enough to implement aggressive supportive care and recognizing it only after irreversible neurological damage has occurred.
Respiratory EHV-1 Symptoms: Cold-Like Signs That Demand Urgent Attention
The most common manifestation of EHV-1 resembles equine influenza or other respiratory infections. Under normal circumstances, these symptoms might warrant observation and routine veterinary consultation. During an active outbreak, they constitute an emergency.
Nasal Discharge in EHV-1: When “Just a Drip” Becomes Concerning
Nasal discharge typically begins clear and watery, progressing to thick, yellow mucus as infection advances. In the early stages, you might notice only occasional clear drainage that could be dismissed as normal. Pay attention anyway.
Any nasal discharge in a horse with recent travel history or potential exposure should prompt immediate isolation and temperature monitoring. Even if the discharge seems minor and the horse appears otherwise normal, remember that EHV-1 shedding often precedes obvious illness. That “minor” nasal drip could represent the earliest stage of an infection that will progress to neurological disease or spread to every horse in your barn.
EHV-1 Cough and Respiratory Changes You Can’t Ignore
Coughing occurs as the virus irritates airways, typically appearing after fever and concurrent with nasal discharge. The cough may be occasional and mild or more persistent and productive. Swollen lymph nodes under the jaw often accompany respiratory symptoms as the immune system responds to upper respiratory infection.
Unlike the explosive, contagious nature of equine influenza, EHV-1 respiratory disease progresses more gradually. This can create false reassurance—”it’s just a little cough, he’s eating fine”—that delays critical intervention.
Lethargy, Depression and Subtle Behavior Changes in EHV-1 Horses
Infected horses frequently appear dull or lethargic, may refuse feed, act depressed, or prefer remaining still rather than moving. These behavioral changes often accompany fever even before respiratory symptoms become obvious.
For owners who know their horses well, subtle personality shifts can be the earliest warning. A normally gregarious horse standing apart from the herd, a typically food-motivated animal showing no interest in grain, or a usually active horse remaining at the back of the paddock all warrant investigation. During outbreak conditions, trust your instincts—if your horse “isn’t acting right,” take a temperature and call your veterinarian.
Neurological EHV-1 (EHM): Symptoms That Signal a Life-Threatening Emergency
While respiratory EHV-1 causes discomfort and requires isolation, the neurological form—Equine Herpesvirus Myeloencephalopathy (EHM)—represents a true emergency where minutes matter. EHM typically develops approximately 7-10 days following initial infection, though neurological signs can appear as early as day 3 or as late as day 14.
The virus damages blood vessels in the brain and spinal cord, causing inflammation, blood clot formation, and tissue death. As damage accumulates, affected horses develop a progressive constellation of neurological deficits. Any neurological symptom, even subtle, requires immediate emergency veterinary intervention.
Hind-End Weakness and Incoordination: The First Neurological Signs of EHM
Hindlimb weakness or incoordination frequently appears first—horses may stumble, drag toes, or sway as if intoxicated (ataxia). Early symptoms can be remarkably subtle: an occasional toe-drag when turning, slight hindquarter swaying when walking, or hesitation when asked to back up.
As the disease progresses, the weakness becomes unmistakable. Affected horses may adopt a “dog-sitting” posture, dropping back onto their haunches, or lean against walls and fences to maintain balance. Some horses appear to stand normally but when asked to move reveal profound incoordination, crossing their hind legs or nearly falling when turning.
Loss of Tail Tone: The Classic “Dead Tail” Sign in EHV-1 Neurological Cases
Loss of tail tone represents a characteristic EHM sign—the horse’s tail hangs limp and it cannot swish or raise the tail normally, sometimes called a “dead tail”. This symptom results from nerve damage affecting the sacral spinal cord segments that control tail movement.
A normal horse constantly adjusts tail position, swishes at flies, and raises the tail when defecating. An EHM-affected horse’s tail hangs motionless regardless of stimulation. Test by gently attempting to lift the tail—normal horses resist this movement, while horses with tail paralysis offer no resistance.
Urinary and Fecal Changes: Critical Neurological Red Flags in EHM
Difficulty urinating or defecating commonly appears alongside other neurological symptoms: owners may observe urine dribbling uncontrollably, bladder distention, infrequent manure passage, or straining with defecation. These signs result from nerve damage affecting bladder and bowel control.
Watch for:
- Urine dribbling continuously or appearing to leak when the horse moves or shifts position
- A distended abdomen suggesting bladder retention
- Reduced manure production despite normal feed intake
- Unusual posturing or straining when attempting to urinate or defecate
- Urine scald on the insides of the hind legs from chronic dribbling
These symptoms indicate serious spinal cord involvement and demand immediate veterinary attention.
Recumbency in EHV-1 Horses: When a Horse Goes Down and Cannot Rise
Severe cases may become recumbent—the horse collapses and cannot rise—representing a dire emergency. Once a horse reaches this stage, prognosis deteriorates dramatically. Horses down for extended periods develop secondary complications including pressure sores, muscle damage, aspiration pneumonia, and colic.
Some horses cycle between periods of weakness where they can stand with assistance and periods of complete collapse. Any recumbency in a horse under observation for EHV-1 neurological disease requires emergency veterinary intervention and often necessitates specialized nursing care including sling support, frequent repositioning, and intensive medical management.
How Fast EHM Progresses: The EHV-1 Neurological Deterioration Timeline
EHM cases can progress rapidly, sometimes within 24-48 hours, meaning a horse showing mild stumbling Monday morning may be completely unable to rise by Tuesday evening. This rapid progression leaves no room for delayed decision-making.
Veterinarians emphasize that with neurological symptoms, “this is where you don’t wait” to seek help. The window for intervention that might prevent permanent damage or death is measured in hours, not days.
Special EHV-1 Risks: Pregnant Mares and Subclinical Shedders
EHV-1 Abortion Risk: Why Pregnant Mares Require Extreme Vigilance
EHV-1 ranks among leading causes of late-term abortion in mares, often occurring without warning. The virus crosses the placenta and infects the fetus, typically triggering abortion between months 7-11 of gestation. In some outbreaks, “abortion storms” affect up to 70% of susceptible mares in a herd.
Any pregnant mare showing fever or respiratory symptoms during an EHV-1 outbreak requires immediate veterinary involvement. If a pregnant mare develops fever or nasal discharge, contact your veterinarian immediately—the virus may be responsible. Even mild, transient fever that might be dismissed in a non-pregnant horse can signal the beginning of an infection that will result in fetal loss days or weeks later.
Subclinical EHV-1 Shedding: The Invisible Threat Inside Your Barn
Some horses show minimal to no symptoms yet still shed infectious virus. These subclinical carriers represent perhaps the greatest challenge in outbreak control because they appear healthy while actively transmitting disease.
A horse displaying only brief fever or appearing slightly “off” is easily overlooked—but during an outbreak, that animal could be a silent carrier initiating a transmission chain. This reality demands heightened vigilance: when in doubt, check temperatures and favor excessive caution over casual observation.
When to Call Your Veterinarian for EHV-1: Non-Negotiable Triggers
During an active EHV-1 outbreak, the threshold for veterinary involvement drops to zero. Any fever in a horse that traveled or was exposed to outside horses warrants immediate veterinary consultation. Specifically:
Call immediately for any of the following:
- Temperature ≥101.5°F in a horse with travel history or potential exposure within the past 21 days
- Any respiratory symptoms (nasal discharge, coughing, swollen lymph nodes) combined with recent travel or contact with unfamiliar horses
- Any neurological sign whatsoever—even subtle toe-dragging, mild swaying, or slight tail limpness
- Urinary or fecal abnormalities suggesting nerve involvement
- Fever or respiratory symptoms in a pregnant mare
- Any symptom in a horse known to have attended a facility or event with confirmed EHV-1 cases
Dr. Jared Janke of Texas A&M advises that any indication of fever combined with hindlimb incoordination, urine dribbling, or diminished tail tone should prompt owners to isolate the horse and contact their veterinarian immediately.
What Happens When You Call About Suspected EHV-1: How to Prepare
When you contact your veterinarian about possible EHV-1, be prepared to provide complete information:
- All observed symptoms with onset timing
- Temperature readings (current and any elevated readings from previous days)
- Complete travel and exposure history for the past 21 days, including events attended, facilities visited, and any known contact with horses that have since become ill
- Vaccination history including dates of last EHV-1 vaccination
- Current management of the affected horse and how many other horses share the property
Immediate EHV-1 Response Steps Your Veterinarian Will Likely Recommend
Isolation: Quarantine the affected horse immediately if not already isolated, placing it in a separate stall or paddock at least 30 feet from other horses. Some veterinarians recommend 60 feet as ideal. The isolation area should have dedicated equipment, separate air space from other horses (not just a stall in a shared barn aisle), and minimal human traffic.
Protective protocols: Caretakers should wear protective clothing including coveralls, gloves, and boot covers when handling the sick horse, and disinfect hands, tools, and boots thoroughly afterward. Handle the isolated horse last in your daily routine, after all other horses have been fed and cared for.
Movement restrictions: Do not transport the horse except under specific veterinary direction. Most veterinary clinics cannot accept horses with suspected or confirmed EHV-1 due to biosecurity protocols protecting other patients. Your veterinarian will likely perform farm calls rather than asking you to transport.
Diagnostic testing: Veterinarians typically collect nasal swabs and blood samples for PCR testing to confirm EHV-1. While awaiting results (typically 24-48 hours), treat the case as if it is confirmed EHV-1: maintain strict isolation and monitor the affected horse plus all others twice daily.
Regulatory notification: Your veterinarian may notify state animal health officials, as neurological EHV-1 (EHM) is often a reportable disease that regulators track during outbreaks. This isn’t punitive—it allows authorities to identify outbreak patterns and implement containment measures.
Why Early EHV-1 Intervention Dramatically Changes Outcomes
Early veterinary intervention significantly improves outcomes, as supportive care including anti-inflammatory medications and intravenous fluids initiated early in illness gives horses better recovery chances if neurological EHM develops.
Beyond individual patient outcomes, catching the first fever or mild case in your barn enables biosecurity measures before more horses fall ill. Dr. Hannah Leventhal of the University of Missouri explains: Fever frequently appears before neurological signs, so identifying that change early allows owners and veterinarians to act quickly and safely. With EHV, time is critical. The sooner fever or behavioral changes are recognized, the sooner intervention can occur and the rest of the herd can be protected.
As one farm advisory emphasized during the current outbreak, “delay is not your friend” when dealing with EHV-1. Better to make ten false-alarm calls about horses that turn out to be fine than to miss the early warnings of a case that progresses to paralysis, recumbency, and death.
How to Build a Practical EHV-1 Response Plan for Your Barn
Every barn should prepare for the possibility of EHV-1 before an outbreak forces reactive decision-making. Post this symptoms checklist in your barn aisle and tack room where everyone can reference it. Ensure all caretakers, boarders, trainers, and regular visitors understand the warning signs and know to report any concerns immediately.
Essential preparations include:
- Temperature monitoring protocol: Establish where thermometers are stored, who is responsible for taking temperatures, and how readings are logged. During high-risk periods (after travel, during regional outbreaks, or when new horses arrive), implement twice-daily checks.
- Isolation area identification: Determine in advance where a sick horse would be quarantined. The area should be at least 30 feet from other horses, with separate air space, dedicated equipment, and biosecurity protocols.
- Communication tree: Ensure everyone knows who to contact if they observe concerning symptoms. This should include the barn manager or owner, the primary veterinarian’s emergency contact information, and backup veterinary contacts.
- Protective equipment inventory: Stock disposable gloves, boot covers, disinfectant, and dedicated cleaning supplies for isolation areas before you need them urgently.
- Education for all handlers: Train everyone who works with horses to recognize normal versus abnormal behavior and temperature, understand transmission routes, and know basic biosecurity principles.
Final Guidance: Trust Your Instincts and Act Immediately on EHV-1 Signs
The current EHV-1 outbreak demonstrates that this virus remains an ever-present threat wherever horses gather. With 80-90% of horses carrying latent infection, any stressor can trigger reactivation and shedding. The horses appearing at your barn gate, standing in the stall next to yours at a competition, or sharing a water trough at a rest stop during transport could be incubating disease.
Your most powerful tools are knowledge and vigilance. Know the symptoms that matter. Monitor temperatures religiously during high-risk periods. Trust your instincts when a horse isn’t acting normal—if something seems off, investigate rather than dismissing concerns.
And when you identify fever, respiratory symptoms, or any neurological sign whatsoever, remember the veterinary consensus: call immediately. Don’t wait to “see how he does overnight.” Don’t assume it’s “probably nothing.” Don’t delay because you’re worried about bothering your veterinarian with a false alarm.
In the calculus of EHV-1 response, false alarms cost nothing. Delayed recognition costs everything.