11/22/2025
Good in-depth guidance from Thal Equine re EHV
EHV-1 OUTBREAK- WHAT YOU SHOULD KNOW
An outbreak of Equine Herpes Virus-1 (EHV-1) that started in Texas has now spread to several neighboring states. Some horses have developed the neurologic form (EHM) and some have been euthanized. There were New Mexico Horses that attended the events and have returned to the state. Those horses are being isolated to prevent spread and are being monitored for signs of disease.
AS OF 11/21/25 there is an infected animal in New Mexico, in Dona Ana County. The horse is isolated and being treated.
We have had many calls here today and people are very concerned. Here's what you need to know to protect your horses.
Expect events to be canceled and postponed as this progresses. Latest info from New Mexico Livestock board- any health certificates for interstate travel: Horses must be examined within 5 days of travel.
TESTING HORSES FOR DISEASE
Thal Equine now offers in-house PCR testing for EHV-1 from naso-pharyngeal swabs, providing rapid results when every hour counts. Early detection is critical for isolating affected horses and preventing spread. Otherwise samples must be sent to a lab for this test. We are willing to take properly prepared samples from other vets.
WHAT IS EHV-1?
Equine Herpes Virus-1 is a common virus that can cause respiratory disease, abortion in mares, and in some cases, the neurologic disease called Equine Herpes Myeloencephalopathy (EHM). The virus damages blood vessels in the brain and spinal cord, leading to coordination problems, weakness, and potentially fatal neurologic signs.
KEY FACTS
• Incubation period (time between exposure to signs of disease): 2-10 days
• Virus shedding: 7-10 days (sometimes longer)
• Spreads through nose-to-nose contact or droplets in a cough from an infected horse, contaminated equipment, hands, and clothing
• Airborne transmission limited to less than 30 feet
-The EHV-1 virus can live quietly in seemingly healthy horses, and then can spread to others.
WATCH FOR THESE SIGNS
• Fever (102°F or higher is commob) - often appears BEFORE neurologic signs
• Nasal discharge
• Lack of coordination or hindquarter weakness
• Leaning against walls or fences for balance
• Lethargy and poor appetite.
• Urine dribbling.
If you see any of these signs, call your vet immediately.
BIOSECURITY- YOU SHOULD IMPLEMENT THIS NOW
IF YOUR HORSE LEAVES YOUR FARM OR IS AT EVENT
• Use your own trailer whenever possible
• Prevent nose-to-nose contact with other horses
• Don't share water buckets, feed buckets, brushes, or any equipment with outside horses.
• Don't let strangers pet or interact with your horses.
WHEN RETURNING HOME
• Clean and disinfect ALL tack, boots, equipment, and grooming supplies with 1:10 bleach.
• Shower and change into clean clothes and shoes
• Isolate horses that were off the farm for AT LEAST 2 weeks at least 30 feet away from others.
• Work with returning horses LAST when doing chores
• Wash hands frequently or wear latex gloves changing between horses
BRINGING IN A NEW HORSE
• Isolate for 2-3 weeks minimum and monitor re**al temperature
• Use dedicated equipment only for the new horse
• Handle the new horse last each day
SHOULD YOU VACCINATE YOUR HORSES?
1. There are no EHV-1 vaccines currently licensed to prevent EHM (the neuro form) but it is still a good idea to keep up to date vaccination for rhino. Talk to your vet about their recommendations.
2. Only afebrile and asymptomatic horses should be vaccinated. Your vet should examine your horse before vaccinating.
3. A certain percent of vaccinated animals will respond with a low-grade fever, lethargy and/or injection site discomfort. That can sometimes confuse the issue- is it a vaccination reaction or the disease?
4. Vaccination should not be considered a substitute for or equivalent to implementation of good biosecurity measures.
HOW TO DISINFECT SURFACES
A 1:10 bleach solution (1 part bleach to 10 parts water) is effective against EHV-1. ALWAYS clean all organic material off surfaces first, then apply disinfectant.
Other effective disinfectants include phenolic disinfectants (1 Stroke Environ®, SynPhenol-3®) or accelerated hydrogen peroxide products (Accel®). They work better than bleach when there is visible organic matter that cannot be cleaned.
TESTING HORSES FOR DISEASE
Thal Equine now offers in-house PCR testing for EHV-1 from naso-pharyngeal swabs, providing rapid results when every hour counts. Early detection is critical for isolating affected horses and preventing spread. Otherwise samples must be sent to a lab for this test.
TREATMENT OF INFECTED HORSES
Treatment includes supportive care with IV fluids, anti-inflammatory drugs, and antiviral medications. Antiviral drugs may decrease the chance of neurologic signs developing. Severe cases require hospitalization and some horses with EHM will not survive even with treatment.
BOTTOM LINE
This virus spreads easily on hands, clothing, and equipment. People are often the carriers. The most important things you can do are:
1. Keep your horse at home if you can. Less movement less chance of disease.
2. Isolate any horse showing signs immediately
3. Wash your hands between every horse contact
4. Don't share equipment between horses
5. Call your veterinarian at the first sign of illness
6. Remember: Handle healthy horses FIRST, sick horses LAST.
Latest info from New Mexico Livestock board- any health certificates for interstate travel: Horses must be examined within 5 days of travel.
For more detailed information on EHM (the neurologic disease), here is something I wrote in Horse Side Vet Guide: https://horsesidevetguide.com/drv/Diagnosis/288/equine-herpes-myeloencephalitis-ehm/
Stay vigilant, practice strict biosecurity, and don't hesitate to call with questions or concerns. This is a serious situation, but with proper precautions, the risk of your horse getting the disease is small.
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References:
1. Texas Animal Health Commission. (2023). Biosecurity Guide: Keeping Your Horses Healthy. Texas Animal Health Commission.
2. Texas Animal Health Commission. (2023). Fact Sheet: Equine Herpes Myeloencephalopathy. Texas Animal Health Commission.
3. Recent update from NMLB
3. Horse Side Vet Guide. Equine Herpes Myeloencephalitis (EHM).
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