A neurological EHV-1 outbreak originating at Texas barrel racing events in November 2025 has spread across eight U.S. states, with 34 confirmed cases and multiple fatalities forcing widespread event cancellations. Understanding exactly how this virus moves—through air, equipment, water, and people—is now critical knowledge for every horse owner, barn manager, and veterinarian navigating the current crisis. This comprehensive guide explains the science behind each transmission route and delivers practical protocols to protect your horses.
EHV-1 Outbreak 2025: What We Know About the Current Spread
The index event traces to the WPRA World Finals and Elite Barrel Race held November 5-9, 2025, at the Extraco Events Center in Waco, Texas, where approximately 1,000 horses gathered from 31 U.S. states and four Canadian provinces. Texas Animal Health Commission officials have described this as a “particularly aggressive strain” characterized by acute presentation, rapid progression, and high clinical severity.
As of November 28, 2025, the Equine Disease Communication Center reports confirmed cases across Texas (16 cases, with 15 showing neurological symptoms), Oklahoma (3 EHM cases), Louisiana (3 EHM cases), Colorado (1 case), New Mexico (3 cases), Arizona (3 cases), and Washington (2 cases). At least two horses have been euthanized, with TAHC noting “several horse deaths suspected to be associated with the virus” that remain unconfirmed pending laboratory testing.
The outbreak has triggered cascading disruptions: the Barrel Futurities of America World Championship was cancelled mid-event, the National Barrel Horse Association suspended sanctioning for all events through December 1, and Texas instituted a 21-day hold on all horses that attended the Waco event. The National Finals Breakaway Roping in Las Vegas was postponed, and the Fort Worth Stockyards Championship Rodeo switched to a bulls-only format. Colorado State University confirmed its first linked case on November 21, and state veterinary offices from Ohio to Florida have issued formal alerts.
Latent EHV-1 Infection: The Hidden Reservoir Behind Major Outbreaks
Before examining how EHV-1 travels from horse to horse, barn managers and owners must understand a fundamental reality: 80-90% of horses are latently infected with EHV-1 by age two. This establishes a vast, invisible reservoir of potential virus throughout the equine population.
Latency means the virus lies dormant within nerve tissue and lymphocytes, escaping detection by standard testing. No commercial test can identify a latently infected horse—PCR testing only detects active shedding at the moment of sampling. When stress triggers reactivation—transport, competition, weather changes, illness, or even the excitement of a show environment—a previously healthy horse can begin shedding infectious virus without displaying any clinical signs.
This explains why outbreaks seem to emerge unpredictably. A latently infected horse, stressed by travel to a competition, reactivates and begins shedding virus. By the time fever appears days later, that horse may have already exposed dozens of others through nose-to-nose contact, shared water, and contaminated equipment. The 2-10 day incubation period (typically 4-6 days, though sometimes as short as 24 hours) creates a window where infected horses actively shed virus before anyone recognizes a problem.
How EHV-1 Spreads Through Direct Contact and Nose-to-Nose Exposure
The most efficient transmission path is exactly what you’d expect: nose-to-nose contact between horses. Dr. Lutz Goehring, an EHV researcher, emphasizes that EHV-1’s main transmission route is “horse to horse—and especially nose to nose direct touching.” When an infected horse touches noses with another, virus-laden nasal secretions transfer directly to the susceptible horse’s respiratory epithelium, where infection takes hold.
Infected horses typically shed virus for 7-10 days after fever onset, though shedding with the neurological form (EHM) may persist for 21-28 days. Critically, horses shed during the incubation period before showing any symptoms. A horse that appears perfectly healthy may already be highly contagious.
Clinical signs progress in a predictable pattern when they appear: fever (often the first and sometimes only sign, typically 101.5°F or higher), followed by nasal discharge, coughing, and lethargy. In horses that develop the neurological form, EHM signs typically emerge 8-12 days after initial infection—hind-end weakness, toe-dragging, difficulty urinating, and in severe cases, inability to rise. The neurological mutation of EHV-1 (the D752 strain) replicates more rapidly and circulates at higher blood levels earlier in disease progression, increasing the risk of severe outcomes.
EHV-1 Aerosol Transmission: How Far the Virus Can Travel
Unlike equine influenza, which spreads explosively through barns within minutes, EHV-1 is what researchers call a “slower, heavier virus” that travels in droplets rather than fine aerosols. This distinction matters enormously for practical biosecurity.
The British Horse Society cites aerosol droplet spread of no greater than 5 meters (approximately 16 feet), while U.S. veterinary sources indicate droplets from coughing or snorting can travel up to 30 feet under certain conditions. Colorado’s Department of Agriculture recommends maintaining 30 feet minimum between tied horses at events, with 60 feet considered ideal.
Environmental conditions affect aerosol persistence. Enclosed spaces like barns and trailers concentrate respiratory droplets, while outdoor settings with air movement dilute and disperse them more rapidly. Indoor stabling during an outbreak dramatically increases transmission risk compared to well-ventilated or outdoor housing.
The good news buried in EHV-1’s physical characteristics: “Distance definitely is our friend,” notes Goehring. Unlike viruses that travel on air currents from one barn corner to another within seconds, EHV-1 requires closer proximity. This makes physical separation between horses genuinely protective—if rigorously maintained.
Fomite Transmission: How Equipment, Tack, and Trailers Spread EHV-1
Any inanimate object that contacts an infected horse’s nasal secretions can become a vehicle for transmission to the next horse. This indirect pathway through fomites represents a major challenge because virus survival on materials can far exceed what most horse owners expect.
How Long EHV-1 Survives on Surfaces, Fabrics, and Barn Materials
Classic research from the 1950s and 60s established that EHV-1 survives 35-42 days on hessian fabric (burlap) and horse tail hair. More recent work confirms the virus persists at least 48 hours on leather, fabric, wood shavings, and polystyrene under laboratory conditions. On hard surfaces like glass, galvanized metal, and wood, survival extends up to 7 days.
For practical daily biosecurity, the Merck Veterinary Manual estimates approximately 48 hours of viability on common surfaces under realistic environmental conditions, though UC Davis notes that functional transmission viability on common fomites may be closer to 4-6 hours. The discrepancy reflects that laboratory survival under ideal conditions exceeds survival when surfaces face UV exposure, temperature fluctuations, and physical disturbance.
The critical takeaway: equipment used on an infected horse yesterday remains potentially infectious today, and possibly for days afterward depending on material and storage conditions.
High-Risk Equipment: Bits, Halters, Lead Ropes and Other EHV-1 Carriers
Items that contact the horse’s mouth and nose carry the highest transmission risk. Bits and bridles directly contact nasal secretions and oral mucus. Halters rest against the nose and chin, and lead ropes—especially those made of manila or other rope materials—can harbor virus for up to a week.
Veterinary sources explicitly identify “shared items that have touched the horse’s mouth or nose such as lead ropes and bits” as transmission vectors. Saddle pads and blankets made of fabric materials remain potentially infectious for 48+ hours after exposure.
At events, the temptation to borrow a forgotten halter or share a lead rope creates real exposure opportunities. The biosecurity rule is absolute: never share equipment that contacts the face, mouth, or nose. Designate color-coded equipment for each horse and keep it separated.
Horse Trailers as EHV-1 Hot Zones: Why They Require Full Disinfection
Horse trailers present particular risk because they create enclosed environments where respiratory secretions accumulate on multiple surfaces—walls, tie rings, rubber mats, dividers. A shared trailer effectively becomes a mixing vessel for viral exposure.
The USDA Animal and Plant Health Inspection Service emphasizes that “horses can contract the virus by coming into contact with contaminated surfaces such as…transport vehicles.” US Equestrian mandates that trailers be “properly cleaned and disinfected between loads of horses, especially those loads containing sick horses.”
Effective trailer disinfection requires complete removal of organic material (manure, bedding, hay), washing with detergent and water, application of disinfectant to all interior surfaces including often-overlooked areas like latches and tie rings, and allowing complete drying before the next use.
EHV-1 Transmission Through Water: Buckets, Troughs and Hoses
Recent research confirms that EHV-1 remains stable and infectious in water across a broad temperature range (4-30°C) and pH range (pH 7-10), surviving up to two weeks under optimal conditions. Sediment in water can even protect viral particles from UV damage, extending infectivity.
This makes communal water sources at shows and events a significant transmission pathway. Shared water troughs, automatic waterers between stalls, and the common practice of dipping hoses into buckets all create opportunities for viral spread.
Protection requires bringing your own buckets and hose, keeping hose ends off the ground and never submerging them in buckets, and never allowing your horse to drink from shared water sources. At multi-day events, this discipline separates farms that escape outbreaks from those caught in their path.
How Humans Spread EHV-1 Between Horses Through Hands and Clothing
While horse-to-horse contact dominates transmission, humans serve as mechanical vectors carrying virus on hands, clothing, and boots between animals. Multiple veterinary sources confirm that “people can spread the virus from horse to horse by contaminated hands and clothing.”
A veterinary hospital outbreak documented spread between physically separated wings despite protocols requiring staff to change clothes and gloves between barns and disinfect equipment after each use. Over 50% of horses became febrile within four days, with transmission attributed to “contaminated hands and clothing of personnel” along with aerosolization. This demonstrates how difficult complete prevention becomes once virus is circulating.
Professionals at Risk: Farriers, Vets, Trainers and the Human Factor in EHV Spread
Anyone moving between multiple horses or farms presents transmission risk: veterinarians, farriers, trainers, exercise riders, feed delivery personnel, and of course owners themselves who visit multiple barns. California’s State Veterinarian specifically warns against sharing “farrier and veterinary equipment” and emphasizes that professionals moving between properties should clean and disinfect all tools.
For barn managers, establishing protocols for outside professionals matters. Request that farriers and veterinarians arrive at your facility first before visiting properties with known or suspected illness. Ask about their biosecurity practices. Provide disinfectant boot baths at entry points.
Hand Hygiene for EHV-1 Prevention: Simple Measures That Stop Spread
The AAEP emphasizes performing hand hygiene “when moving between horses that are grouped separately to avoid spreading pathogens that may contaminate your hands.” Practically, this means washing hands with soap for at least 20 seconds or using alcohol-based hand sanitizer after touching each horse, especially before moving to another.
At competitions, carry sanitizer and use it religiously. The few seconds this takes after each horse contact may prevent carrying virus from an infected animal you didn’t know was shedding to your own horse waiting at the trailer.
Biosecurity Measures That Stop EHV-1: What Actually Works
With transmission routes understood, prevention becomes a matter of disciplined implementation.
21-Day Isolation Protocols for Returning or Exposed Horses
The AAEP recommends 21-day isolation for new horses or those returning from events, with 28 days as the standard for premises where EHM has been confirmed. During isolation, returning horses should have restricted access to other horses, dedicated equipment used only for them, and twice-daily temperature monitoring.
Feed and care for isolated horses last, after handling resident horses, to prevent carrying any potential contamination toward the main herd. Change clothing or at minimum thoroughly sanitize hands and clean footwear after completing isolation area chores.
Temperature Monitoring: The Earliest Detection Method for EHV-1
Fever frequently precedes other clinical signs by days. Twice-daily temperature monitoring using dedicated thermometers for each horse (or single thermometers thoroughly disinfected between horses) provides the earliest practical warning that something is wrong.
Normal equine temperature ranges from 99-101°F. Any reading at or above 101.5°F warrants immediate concern and veterinary consultation. Document temperatures in a log kept on each stall door for easy reference.
How to Disinfect Barns, Trailers, and Equipment to Kill EHV-1
EHV-1 is readily killed by common disinfectants when used correctly. The challenge lies in the qualifier “correctly”—disinfectants require clean surfaces and adequate contact time to work.
Step one: Remove all organic material. Bleach and most other disinfectants are inactivated by manure, bedding, and other organic matter. Scrub surfaces with detergent and water first, then rinse.
Step two: Apply appropriate disinfectant. Effective options include household bleach at 1:10 dilution (approximately 5 tablespoons per gallon of water), phenolic compounds such as 1 Stroke Environ or TekTrol, accelerated hydrogen peroxide products like Accel or Intervention, and peroxygen compounds like Virkon S.
Step three: Allow adequate contact time. Surfaces must remain wet with disinfectant for the time specified on the product label—typically a minimum of 10 minutes for bleach. Solutions that dry before contact time is complete won’t achieve disinfection.
Prepare bleach solutions fresh daily to weekly, as they degrade rapidly. Never mix bleach with other chemicals—this creates toxic gases.
Event Biosecurity: How to Protect Your Horse at Shows and Competitions
Before arriving: Confirm your horse is healthy with no fever or respiratory signs. Ensure EHV-1 vaccination is current (within 6 months, understanding that vaccination doesn’t prevent infection but may reduce shedding). Pack your own buckets, hose, hay nets, grooming tools, and thermometer.
At the event: Maintain minimum 30-foot distance from unknown horses. No nose-to-nose greetings. Don’t share any equipment. Avoid communal water. Monitor temperature twice daily. If your horse develops fever while at an event, isolate immediately and contact your veterinarian.
After returning: Isolate your horse from others on your property for at least 21 days. Continue twice-daily temperature monitoring. Clean and disinfect your trailer before using it again. Disinfect all equipment used at the event.
EHV-1 Vaccination: What Research Shows About Protection and Limits
Currently licensed EHV-1 vaccines do not prevent the neurological form of disease. The 2024 American College of Veterinary Internal Medicine consensus statement is unambiguous: “No evidence that available EHV-1 vaccines fully protect against viremia or prevent equine herpesvirus myeloencephalopathy.”
This doesn’t mean vaccination lacks value. Vaccines appear to reduce respiratory disease severity and may decrease viral shedding, potentially lowering transmission pressure in populations that commingle frequently. The AAEP recommends vaccination at 6-month intervals for horses that travel or show regularly.
However, vaccination alone cannot prevent outbreaks. The current vaccines, essentially unchanged for 40 years, don’t fully match the challenge of a virus that has evolved sophisticated mechanisms for immune evasion. Biosecurity remains the essential complement—and during outbreaks, the primary defense.
Importantly, exposed or symptomatic horses should not be vaccinated. A concerning finding from the 2011 Ogden outbreak showed horses were 3.3 times more likely to develop EHM if vaccinated against EHV-1 within five weeks of the event. The interaction between recent vaccination and acute exposure remains incompletely understood.
What Past EHV-1 Outbreaks Teach Us About Stopping Transmission
The 2011 National Cutting Horse Association outbreak in Ogden, Utah, infected over 2,100 horses across 242 facilities in 19 states and one Canadian province. Ninety horses developed confirmed EHV-1/EHM; thirteen died or were euthanized. The pattern was instructive: horses exposed at the event returned home and spread infection to herdmates, creating secondary and tertiary waves of exposure that forced cancellation of horse shows coast to coast.
A veterinary hospital outbreak in the Netherlands demonstrated transmission despite dedicated biosecurity protocols, with virus spreading between physically separated wings through contaminated hands and clothing of personnel. Even with staff changing clothes and gloves between barns and disinfecting equipment after each use, over half of horses became febrile within four days, and 15% developed neurological symptoms.
These cases underscore that perfect prevention is impossible once virus begins circulating in a population. The goal becomes limiting spread through layered protections—distance, hygiene, equipment dedication, and isolation—while accepting that no single measure provides complete protection.
How to Make EHV-1 Biosecurity Sustainable in Real-World Barns
The protocols described here work, but only if implemented consistently. The barn that maintains rigorous biosecurity for two weeks then relaxes remains vulnerable. The key lies in building habits that become automatic rather than requiring constant vigilance.
Color-code equipment so each horse’s bucket, halter, and grooming tools are immediately identifiable. Mount hand sanitizer dispensers at convenient locations. Make temperature logging part of daily feeding routine rather than a special task. Position boot disinfectant mats at natural entry points. These environmental modifications reduce the cognitive burden of biosecurity, making consistent compliance more achievable.
During the current outbreak, many owners face difficult decisions about whether to attend scheduled events. The AAEP recommends consultation with veterinarians about travel risks and emphasizes that movement of horses should be minimized during active outbreaks. US Equestrian continues supporting licensed events with enhanced biosecurity measures, but the risk calculus differs for each owner depending on their horse’s vaccination status, the event’s biosecurity protocols, and their own capacity to implement 21-day isolation upon return.
Final Takeaways: How EHV-1 Spreads and How to Protect Your Horses
EHV-1 spreads through multiple pathways that together create a formidable challenge: direct nose-to-nose contact between horses, aerosol droplets traveling up to 30 feet, contaminated equipment and water sources harboring virus for hours to weeks, and human hands and clothing carrying infection between animals. The current outbreak demonstrates how quickly the virus can disseminate when horses from dozens of states gather, then return home.
Protection requires understanding and addressing each transmission route. Maintain physical distance between horses, especially at events. Never share equipment that contacts the face, mouth, or nose. Bring your own water supplies. Practice rigorous hand hygiene. Isolate returning horses and monitor temperatures twice daily. Disinfect trailers and equipment properly, remembering that organic material must be removed before disinfectants can work.
No vaccine prevents the neurological form of disease, making biosecurity not a supplement to medical prevention but the primary defense. The 80-90% latent infection rate in the general horse population means potential virus circulates invisibly everywhere horses gather. Stress from transport and competition can trigger reactivation and shedding in horses that appeared healthy days earlier.
The discipline required is substantial, but the alternative—watching a beloved horse develop ascending paralysis, struggle to rise, and potentially face euthanasia—makes every bucket brought from home, every hand sanitized between horses, and every day of post-event isolation worthwhile.