Practice Good Biosecurity to Guard Your Equine from EHM |

Practice Good Biosecurity to Guard Your Equine from EHM

Clinical Signs

Clinical signs of EHM in horses may include:

Fever of 102°F or greater. Fever most often comes before neurologic signs

nasal discharge

lack of coordination

hindquarter weakness

leaning or resting against a fence or wall to maintain balance


urine dribbling

head tilt

diminished tail tone

penile paralysis

Consult your veterinarian if your horse exhibits any of these signs.

Practice Good Biosecurity to Guard Your Equine from EHM

Please be aware Equine Herpes Myeloencephalopathy (EHM), the neurologic disease linked to Equine Herpes Virus (EHV-1), was confirmed in a Glasscock County Quarter Horse on April 16, 2019. This is the second case of EHM in Texas this year.

The positive horse attended a seven-day event at the Brazos County Expo center in Bryan, Texas starting on April 1. Following the event, the horse attended a three-day barrel racing event at the Taylor County Expo Center in Abilene, Texas starting on April 12. At that time, the expo center was also hosting a Region II high school rodeo event. The premises where the EHM positive horse originates is under quarantine and the horse is under the care of a Brazos County veterinary hospital. To learn more visit

Texas Animal Health Commission (TAHC) would like to encourage owners of horses potentially exposed to take precautions. Exposed horses should be isolated and have their temperatures monitored twice daily for at least 14 days after last known exposure. If an exposed horse develops a fever or other signs consistent with EHM, diagnostic tests may be performed. Owners should work with their veterinary practitioners to establish appropriate monitoring and diagnostic plans for any potentially exposed horse(s).

What is EHM?

Equine Herpes Myeloencephalopathy (EHM) is a neurologic disease of horses linked to the Equine Herpes Virus (EHV-1). EHV-1 in horses can cause respiratory disease, abortion, and neonatal death. Neurological signs appear as a result of damage to blood vessels in the brain and spinal cord.

EHV-1 is easily spread and usually has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may continue longer in infected horses. For this reason, a 21-day isolation period of confirmed positive EHM cases is suggested.

How EHM is Spread

Horse-to-horse contact, short distance aerosol transmission and contaminated hands, equipment, tack and feed all have a role in disease transmission. Direct and indirect contacts are most important for transmission since the size of the virus limits capacity for airborne transmission to distances of less than 30 feet.


Practice and enforcement of biosecurity measures on equine premises can help prevent the spread of EHV-1. Consistent biosecurity practices must be taken to reduce the risk of disease spread. For more information on biosecurity measures you can take to keep your horses healthy, visit

Key to disease control is the immediate separation and isolation of identified suspect cases. Ideally, a person caring for a sick horse should not also work with healthy horses. If this is impractical, always handle healthy horses first and sick horses last.

People can easily transmit this virus on their hands and clothing. Individuals should wash their hands thoroughly with soap and hot water between contacts with horses to reduce risks of disease spread. Wearing disposable gloves and changing them between horses or use of hand sanitizers between horse contacts are other alternatives. When handling any sick horses suspected to have EHV-1 infection, it is imperative that halters, bridles, and other tack not be shared with stablemates. Feed and water buckets should also be dedicated to sick horses and not shared within a stable.


Herpes viruses can be treated by many disinfectants. A 1:10 dilution of bleach in water is effective against EHV-1. All areas must be thoroughly cleaned of dirt, plants, and animal waste before the use of these products. Use soaps or detergents to clean the area before applying a disinfectant.

In barn environments, where organic material (dirt, plants, animal waste, etc.) cannot be completely removed, it is suggested to use a disinfectant that retains activity in the presence of organic matter. Phenolics, such as 1 Stroke Environ® or SynPhenol-3®, and accelerated hydrogen peroxide products, such as Accel®, have this property. Be sure to follow manufacturers’ recommendations and label instructions for all disinfectants.

*TAHC does not endorse any of the listed disinfectant products.

Additional Resources:

–Texas Animal Health Commission