11/21/2025
For all, Dr. Jen Gold DVM, DACVIM shared this with us. We know this is a scary time but the best thing to do is stay home and educated yourself!
Dr’s at VetweRx are here for any questions and concerns!
What is Equine Herpes Virus?
Equine herpesvirus (EHV) is a family of equine viruses named by numbers including EHV-1, 2, 3, 4 and 5. The ones that carry the most risk for horses is EHV-1, 4. EHV-3 causes with a disease called co**al exanthema which is a venereal disease spread amongst horses.
EHV-1 and EHV-4 most frequently cause respiratory disease which is typically mild and self-limiting. EHV-1 and very rarely EHV-4 can cause equine herpesvirus myeloencephalopathy (EHM) neurologic form of equine herpesvirus). The disease causes damage to the neurologic blood vessels in spinal cord and brain and can be fatal, although most horses recover
Horses can be carriers of EHV with no clinical signs and can spread the disease to other horses. Testing and quarantining affected horses in isolation is the primary way to control the disease. Vaccines are available but do not completely prevent any form of the disease, but it is important to understand that the vaccine does not prevent the neurologic form of EHV.
Clinical Signs:
EHV-1: Fever (temperature greater than 101.5o F), the fever is not consistent it comes and goes, nasal discharge, lethargy, obtundation, late term abortion, neonatal death, neurologic disease (ataxia, inability to urinate, defecate, head pressing, recumbency).
EHV-4: Fever (temperature greater than 101.5o F), Don’t forget the fevers come and go so not present all the time. nasal discharge, lethargy, late term abortion, neonatal death, very rare neurologic disease.
Nasal shedding of the virus can last for up to 10-14 days post infection.
The incidence rates of EHM and abortion caused by EHV are approximately 10%. The majority of cases recover.
Diagnosis: Nasal swab or centrifuged blood for qPCR testing. Viral isolation from blood or increase in antibody titers in serum samples collected 2-3 weeks apart. PCR remains the quickest, to do but realize it is testing for presence of the virus and doesn’t predict neurologic disease.
Treatment: Supportive care and rest are the best treatments. Flunixin or phenylbutazone for fever and inflammation. In some cases, with neurologic signs valacyclovir (anti-viral) and heparin can be used for treatment.
Prevention: Vaccinations help prevent respiratory and abortive forms of EHV-1, 4. Again as stated above there is no vaccine to prevent the neurologic form of EHV-1.
Protection is best done by maintaining current vaccinations of all animals on the property and to follow biosecurity protocol when bringing new horses onto premises or when traveling. Vaccinating during an outbreak does not prevent EHM from occurring.
Biosecurity: EHV is spread by aerosolized particles from nasal discharge or from contaminated surfaces including people, clothing, feed and water buckets, troughs, sharing of bridles and other equipment. Isolation is key to preventing spread of the virus.
The virus dose not stay in the environment for long periods; proper biosecurity includes extensive disinfection of equipment and surfaces that come in contact with affected horses.
It’s best to use a solution of 1 part chlorine bleach to 10 parts water or accelerated hydrogen peroxide disinfectants are effective for decontaminating equipment and environment.
Biosecurity at equine facilities or events: Limit horse to horse contact, limit horse to human to horse contact. Avoid use of communal water sources. Do not dunk hoses into water buckets when filling them. Avoid sharing of equipment unless thoroughly cleaned and disinfected between uses. Monitor horses for signs of EHM including fevers, nasal discharge, cough, dark red mucous membranes, swollen eyes, swollen legs and acute onset of neurologic signs.
As of right now The Equine Disease Communication Center is monitoring the outbreak of EHM that originated at the Women’s Professional Rodeo Association (WPRA) World Finals and Elite Barrel Race event Nov 5-9. (https://www.equinediseasecc.org/)
To date, officially confirmed cases have been reported in the following states:
EHV-1 cases - PCR positive, no neurologic signs
Texas: 5
Oklahoma: 2
Louisiana: 3
EHM cases - PCR positive, with neurologic signs
Colorado: 1
The EDCC website is https://www.equinediseasecc.org/ and keeps updating on the cases and how things are being handled.
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