11/19/2025
In light of the recent EHV-1 outbreak at BFA in Oklahoma-
EHV-1- What is it and what to do about it
What is it?
EHV-1, also known as Equine Rhinopneumonitis, is a respiratory virus that can mutate into a neurologic form in some horses (called Equine Herpes Myeloencephalopathy, or EHM). There is usually a fever associated with it (a fever is a temperature over 101.5F in an adult horse), and it frequently shows respiratory symptoms (coughing, nasal discharge, enlarged lymph noted) as well as systemic signs (lethargy and decreased appetite). When this virus mutates to EHM, it presents with neurologic signs and urine dribbling.
How is it spread?
EHV-1 is spread in direct horse to horse contact, mostly through respiratory secretions. This can mean shared spaces, shared equipment, and shared people. Respiratory secretions can travel up to 30 feet between horses, and the virus can live up to 30 days on surfaces.
Vaccination:
The Flu/Rhino vaccine does build effective immunity against EHV-1, but it does not provide complete protection against EHM. The vaccine can reduce virus shedding from your horse and may be able to reduce the virus load. If your horse is vaccinated it does not guarantee that your horse will not get EHV-1 or EHM. However, it does have theoretical value against EHM (by reducing viremia), and certainly against spread of the virus by reducing viral shedding in the environment. Still, the most effective way to prevent your horse from contracting this virus is through biosecurity/isolation from other horses.
Testing:
EHV-1 is tested through blood or nasal swabs. It is not necessary to test horses not showing symptoms and that have not been exposed to the virus. If you think your horse has become infected, place them on strict quarantine and schedule an appointment to get them tested 72 hours after their initial fever (testing sooner after a fever may result in a false negative).
How to protect your horse and your barn:
Reduce exposure: If horses from your farm have travelled to any areas or shows that are in the same area as the reported outbreak (Oklahoma, Texas), quarantine them for at least 2 weeks
Take temperatures: in many cases, horses develop a fever 24 hours before they begin shedding the virus. Be diligent in observing your horses for any change in behavior and take temperatures consistently (at least twice per day) if you are worried about exposure or transmission. IF THEY HAVE A FEVER OVER 101.5, ISOLATE THEM from other horses immediately.
Vaccinate: If you are going to any shows in the near future and your horses havenโt been vaccinated for Flu/Rhino in the last 6 months, schedule a booster vaccine >7-10 days prior to leaving for your show is ideal.
Biosecurity: If you do go somewhere with your horse, be sure to keep your equipment separate. Avoid working during high traffic times and direct contact between horses.
If you plan to take your horse to any shows in the near future, please reference the show guidelines and make sure you are in compliance with their vaccination and health certificate requirements; be aware that their requirements may change rapidly as this situation develops.
For more details from AAEP about EHV-1, please visit:
https://aaep.org/wp-content/uploads/2024/02/EHV1-4-guidelines-2021.pdf
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