11/22/2025
Equine EHV-1.
Everyone has read about the EHV-1 outbreak in Texas and Oklahoma that started at the women’s professional rodeo association in Waco, Texas.
Please be cautious and critical of what you read on social media. Information is good, panic is bad.
Virtually all horses have been exposed to this virus and can have a positive blood titer if tested, and do not get sick. The virus does stay in the body, and during periods of stress can cause illness, without a new exposure. It has been shown that old horses have more serious complications in these cases than younger horses. We have read about the case in St. Mary’s County Maryland. I do not personally know this Horse or Owner or Farm. But official sources have confirmed this is an unrelated case to the current outbreak in the west. Most likely this horse was a horse that had the virus in its system and for some reason it reactivated and caused a severe illness that the horse did not survive. Due to the power, often bad, of social media there is no need for the owner or farm to be identified. The state does do contact tracing. So if there was any exposure, you would be notified. 
With hundreds of horses at the competitions in Texas, and Oklahoma, there will surely be many more cases in the next week or two. We do not know yet how widespread this outbreak will be due to the number of horses and how far these horses travel to competitions around the United States.
The best protection against spreading this disease is identification, isolation and quarantine.
If you go to competitions or events with lots of horses at a location, It is always good practice to take temperatures daily or twice a day. Low-grade fevers of 101.5 are often in the first signs of EHV-1. Knowing your horses normal temperature is important. Horses are usually about 100.0, but some run low and their normal temperature is 99.0. So a degree and a half above their normal daily temperature is something to be of concern. Early identification and quarantine is the most important thing. “Healthy” horses can be infectious and spread the disease before they are noticed to be sick.
The EHV-1 virus can cause respiratory disease, abortions, and EHM the neurologic form. Our vaccines protect against respiratory disease and abortion. There is no vaccine for the neurological form. Vaccines do decrease the shedding of virus in healthy horses, so can help decrease the viral load in the environment. This potentially helps decrease all diseases from EHV-1. This is why proof of vaccines are required at many events.
Bay Equine normally vaccinates for Flu and EHV rhino twice a year.
Spread of the virus is through Contact. It does not live more than a few hours in the environment. However, communal water troughs can be a common source of spread. Temperatures and moisture contribute to how long viruses live in the environment.
You can think of it a little bit like Covid. If you drink from the same glass, or water bucket, as someone else you could be exposed. If you are very close in a car or around a dinner table, or in stalls across from each other, or tied next to each other, you could expose each other. You, or your horse, can look healthy, but still be contagious. If you go into a stall immediately after an infected horse leaves, you could be exposed. If you enter that stall 24 hours later, probably not.
Horses usually show signs within one to three days of exposure. But this can be as subtle as a 1.5° temperature increase which you wouldn’t notice without a thermometer.
I will try to post more later. But the take away messages now are:
1. Take temps regularly. Know your horses normal temp and keep a log in writing.
2. Be aware of your surroundings. Pay attention to water sources, and distance from other horses. If you’re using a stall at an event, when was the last time a horse was in there. If you’re not required to bring a health certificate, then no one else is either. 
3. Just because we had one isolated case in Maryland, does not mean we are at high risk like Texas and Oklahoma and some of the western states at this time. 
4. Social media can be very good, and very bad. We all know this. Just remember not everything you read is true or accurate.
Most of you know, I also ride and compete and trailer to endurance rides in many states. So I’m in this with you professionally and personally.
Dr Linda Molesworth

