Rio Grande Horse Hotel

11/22/2025

𝐄𝐇𝐕-𝟏 𝐚𝐧𝐝 𝐄𝐇𝐌 𝐒𝐞𝐫𝐢𝐞𝐬: 𝐅𝐚𝐜𝐭𝐬 𝐨𝐧 𝐭𝐡𝐞 𝐃𝐢𝐬𝐞𝐚𝐬𝐞

EHV-1 (Equine Herpesvirus 1) and EHM (Equine Herpesvirus Myeloencephalopathy) are presently causing a significant amount of distress in the western performance horse industry. Though this is not a new disease, it is more novel to this group of horses.

EHV-1 has four different forms - respiratory, neonatal (foal) infection, abortion and neurologic. The neurologic form can cause what is called EHM, which is the most serious and potentially fatal form of disease. The respiratory form is more commonly diagnosed. Clinical signs include fever, nasal discharge (snotty nose) and/or cough.

EHM is the most severe form of the virus and the reason why these outbreaks are so significant. In this form, the virus will attack the brain and spinal cord and can be fatal to the horse. In addition to those listed above, clinical signs that are noted with the neurologic form include quick-onset weakness, uncoordiantion and trouble standing. They may have difficulty with bowel movements and urination. Some horses also experience extreme lethargy and comatose-like states.

𝐓𝐡𝐞 𝐓𝐋, 𝐃𝐑?

- Horses can be infected with EHV-1 and not suffer from neurologic disease (EHM)
- The virus is transmitted through horse-to-horse contact, contaminated humans/tack/equipment and briefly in the air
- There can be “silent carriers” who do not show clinical signs, but can still shed the virus and infect other horses - meaning it is easier to transmit
- The incubation period is variable - on average its 4-7 days from exposure, but it can take up to 14 days
- The best early detection protocol for potentially exposed horses is to take temperatures twice daily - anything above 101.5 degrees is a fever
- If your horse has a fever or displays any other clinical signs of disease (cough, snotty nose, lethargy, inappetance, incoordination), it should be separated from other horses and you should consult your veterinarian for further diagnostics and treatment
- The best prevention for transmission is to stay home and not be in contact with other horses while this outbreak is occurring

𝐇𝐨𝐰 𝐜𝐚𝐧 𝐰𝐞 𝐝𝐢𝐚𝐠𝐧𝐨𝐬𝐞 𝐢𝐭?

Your veterinarian can send nasal swabs and blood samples to laboratory testing facilities that run PCR (polymerase chain reaction). Bend Equine Medical Center additionally has an on-site test available for potential cases or exposed horses (results available in 1 hour); you do not need to be a current client to run the tests. This disease is reportable, so if a positive case is identified then it is required to be reported to the state vet.

𝐈𝐬 𝐢𝐭 𝐭𝐫𝐞𝐚𝐭𝐚𝐛𝐥𝐞?

Though there is not a specific medication to treat the virus, supportive care can be administered. These include anti-inflammatories, IV fluids and slings for horses that are unable to stand. Antibiotics will not have an effect and anti-virals have been shown to have minimal effect in horses that are already clinically affected by the virus. The mortality rate of EHM (neurologic form) is 30-50% with extremely variable recovery times - horses that are able to stay standing on their own typically have a better overall prognosis than down horses. The majority of cases that are infected with EHV-1 (and do not get the neurologic strain) develop a fever +/- nasal discharge and recover. Quarantined horses/facilities are recommended to stay isolated for 21 days after the last positive case is identified.

𝘐𝘴𝘰𝘭𝘢𝘵𝘪𝘰𝘯 𝘰𝘧 𝘱𝘰𝘵𝘦𝘯𝘵𝘪𝘢𝘭𝘭𝘺 𝘪𝘯𝘧𝘦𝘤𝘵𝘦𝘥 𝘰𝘳 𝘦𝘹𝘱𝘰𝘴𝘦𝘥 𝘩𝘰𝘳𝘴𝘦𝘴, 𝘤𝘦𝘢𝘴𝘪𝘯𝘨 𝘮𝘰𝘷𝘦𝘮𝘦𝘯𝘵 𝘪𝘯 𝘢𝘯𝘥 𝘰𝘶𝘵 𝘰𝘧 𝘧𝘢𝘤𝘪𝘭𝘪𝘵𝘪𝘦𝘴 𝘵𝘩𝘢𝘵 𝘩𝘢𝘷𝘦 𝘩𝘢𝘥 𝘦𝘹𝘱𝘰𝘴𝘦𝘥 𝘪𝘯𝘥𝘪𝘷𝘪𝘥𝘶𝘢𝘭𝘴 𝘰𝘳 𝘨𝘳𝘰𝘶𝘱𝘴 𝘢𝘯𝘥 𝘴𝘦𝘦𝘬𝘪𝘯𝘨 𝘪𝘮𝘮𝘦𝘥𝘪𝘢𝘵𝘦 𝘷𝘦𝘵𝘦𝘳𝘪𝘯𝘢𝘳𝘺 𝘢𝘵𝘵𝘦𝘯𝘵𝘪𝘰𝘯 𝘪𝘧 𝘢𝘯𝘺 𝘩𝘰𝘳𝘴𝘦𝘴 𝘥𝘪𝘴𝘱𝘭𝘢𝘺 𝘤𝘭𝘪𝘯𝘪𝘤𝘢𝘭 𝘴𝘪𝘨𝘯𝘴 𝘪𝘴 𝘪𝘮𝘱𝘦𝘳𝘢𝘵𝘪𝘷𝘦 𝘵𝘰 𝘳𝘦𝘥𝘶𝘤𝘪𝘯𝘨 𝘴𝘱𝘳𝘦𝘢𝘥 𝘰𝘧 𝘵𝘩𝘪𝘴 𝘥𝘪𝘴𝘦𝘢𝘴𝘦.

𝐂𝐚𝐧 𝐰𝐞 𝐯𝐚𝐜𝐜𝐢𝐧𝐚𝐭𝐞 𝐚𝐠𝐚𝐢𝐧𝐬𝐭 𝐄𝐇𝐕?

The short answer is, partially. The Pneumabort-K vaccine can reduce viremia and viral shedding. Flu/Rhino combo vaccine (eg. FluVac Innovator EHV4/1) will prevent the respiratory forms of EHV. Unfortunately, studies are somewhat divided on recommendations for vaccinating in the face of an outbreak, so it is easy to read differing opinions on the matter. 𝘛𝘩𝘦𝘳𝘦 𝘪𝘴 𝘯𝘰 𝘷𝘢𝘤𝘤𝘪𝘯𝘦 𝘵𝘩𝘢𝘵 𝘩𝘢𝘴 𝘣𝘦𝘦𝘯 𝘴𝘩𝘰𝘸𝘯 𝘵𝘰 𝘱𝘳𝘦𝘷𝘦𝘯𝘵 𝘵𝘩𝘦 𝘯𝘦𝘶𝘳𝘰𝘭𝘰𝘨𝘪𝘤 𝘧𝘰𝘳𝘮 - 𝘌𝘏𝘔. Additionally, there has been some evidence showing that horses that are in a stressed state that receive the vaccine may be more likely to contract the disease.

The only horses that should be vaccinated during an active outbreak are unexposed, afebrile and asymptomatic individuals. Fevers can occur after vaccination, which can make it more difficult to identify individuals that need to be isolated. 𝘝𝘢𝘤𝘤𝘪𝘯𝘢𝘵𝘪𝘰𝘯 𝘪𝘴 𝘯𝘰𝘵 𝘢 𝘴𝘶𝘣𝘴𝘵𝘪𝘵𝘶𝘵𝘦 𝘧𝘰𝘳 𝘨𝘰𝘰𝘥 𝘣𝘪𝘰𝘴𝘦𝘤𝘶𝘳𝘪𝘵𝘺 𝘮𝘦𝘢𝘴𝘶𝘳𝘦𝘴, 𝘲𝘶𝘢𝘳𝘢𝘯𝘵𝘪𝘯𝘦 𝘢𝘯𝘥 𝘪𝘴𝘰𝘭𝘢𝘵𝘪𝘰𝘯.

_______________________________

I hope this general overview has helped provide some clarity on this disease. I will do a separate post containing more information on current travel recommendations, health certificate requirements and additional information as we receive it. Even though there have not been positive cases identified in Oregon at this time, staying up to date with current and 𝐜𝐨𝐫𝐫𝐞𝐜𝐭 information will be the best way to prevent unnecessary spread of this disease.

Please write any questions or topics you’d like me to follow up on in the comments. Thank you for your time spent reading this!

-Dr. Cooper

11/22/2025

Now EHM (EHV-1) is in southern New Mexico! 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 by vet within 5 days of travel.

It's even more critical to:

1. Keep your horses where they are if possible- minimize transport.
2. Avoid contact with strange horses. You can act as a source of infection for your horses . Wear gloves, wash your hands frequently.
3. Remember that equipment and tack, shoes and clothing can all harbor the virus and potentially infect another horse.
3. Ensure your horses are up to date with flu/rhino vaccine (although not protective against EHM).

SIGNS TO WATCH FOR

--Nasal discharge
--Fever (102°F or higher is common) - often appears BEFORE neurologic signs
--Lack of coordination or hindquarter weakness
--Leaning against walls or fences for balance
--Lethargy and poor appetite.
-- Urine dribbling.

TESTING HORSES FOR DISEASE

Thal Equine now offers in-house PCR testing for EHV-1 from properly sampled 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 samples from other vets.

The Equine disease communication center is a good site for keeping up with the situation. https://equinediseasecc.org/news/article/Equine-Herpesvirus-Myeloencephalopathy-(EHM)-Outbreak

11/22/2025

ANIMAL HEALTH ALERT FROM THE NEW MEXICO LIVESTOCK BOARD: The Texas Animal Health Commission and Oklahoma Department of Agriculture, Food, and Forestry have confirmed equine herpes myeloencephalopathy (EHM), the neurologic disease linked to equine herpesvirus (EHV-1) on Nov. 18 following equine events in their respective states. These events were attended by horses from many states, including New Mexico.

For more information from the New Mexico Livestock Board, visit https://www.nmlbonline.com/news. For NMDA's EHV-1 fact sheet, visit https://nmdeptag.nmsu.edu/media/pdf/EHV-1-factsheet.pdf.

11/22/2025

𝐄𝐇𝐕-𝟏 𝐚𝐧𝐝 𝐄𝐇𝐌 𝐒𝐞𝐫𝐢𝐞𝐬: 𝐂𝐮𝐫𝐫𝐞𝐧𝐭 𝐭𝐫𝐚𝐧𝐬𝐩𝐨𝐫𝐭 𝐫𝐞𝐜𝐨𝐦𝐦𝐞𝐧𝐝𝐚𝐭𝐢𝐨𝐧𝐬 𝐚𝐧𝐝 𝐫𝐞𝐪𝐮𝐢𝐫𝐞𝐦𝐞𝐧𝐭𝐬

The initial outbreak of EHV-1 with an EHM (Equine Herpes Myeloencephalopathy) form occurred after a Women’s Professional Rodeo Association (WPRA) World Finals event in Waco, TX (Nov. 5-9). After this event, many of the same horses attended other events in TX and OK before experiencing any clinical signs (average of 4-7 day incubation period), which is what contributed to the multi-state spread of this disease. After the BFA event in Guthrie, OK was cancelled, owners were advised to leave the premises, bringing potentially exposed horses back to their home states and is another reason why we are seeing the disease in so many areas now.

As of 12:00pm on 11/21/2025, there are 15 confirmed cases of EHM and 1 confirmed case of EHV-1 without neurologic signs in the states of Texas, Oklahoma, Louisiana, Colorado and New Mexico. There is one unrelated case (not associated with this event/outbreak) reported in Maryland. There are many other horses undergoing testing without confirmed, reported numbers at this time.

So, what does this mean for current travel recommendations, health certificate requirements and upcoming events?

𝐀𝐫𝐢𝐳𝐨𝐧𝐚 & 𝐍𝐞𝐯𝐚𝐝𝐚 𝐃𝐞𝐩𝐚𝐫𝐭𝐦𝐞𝐧𝐭 𝐨𝐟 𝐀𝐠.: Horses that have been at the following locations will not be allowed entry into the state for 21 days following potential exposure even if they are not symptomatic if they have been on the following premises (subject to change):

- Extraco Events Center (Waco, TX)
- 377 Arena (Stephenville, TX)
- Lazy E Arena (Guthrie, OK)
- Jackson County (Edna, TX)

Health certificates for the horses traveling into these states will require a statement from the veterinarian filling out the health certificate stating that the horse has not been on one of these premises (or any that come up with an EHV-1/EHM positive case) for the 21 days leading up to the date of the health certificate.

𝐘𝐨𝐮𝐫 𝐭𝐲𝐩𝐢𝐜𝐚𝐥 𝟑𝟎 𝐝𝐚𝐲 𝐡𝐞𝐚𝐥𝐭𝐡 𝐜𝐞𝐫𝐭𝐢𝐟𝐢𝐜𝐚𝐭𝐞 𝐰𝐢𝐥𝐥 𝐧𝐨𝐰 𝐨𝐧𝐥𝐲 𝐛𝐞 𝐯𝐚𝐥𝐢𝐝 𝐟𝐨𝐫 𝟓 𝐝𝐚𝐲𝐬 𝐢𝐟 𝐭𝐡𝐞 𝐬𝐭𝐚𝐭𝐞 𝐲𝐨𝐮 𝐚𝐫𝐞 𝐭𝐫𝐚𝐯𝐞𝐥𝐢𝐧𝐠 𝐟𝐫𝐨𝐦 𝐡𝐚𝐬 𝐡𝐚𝐝 𝐚 𝐩𝐨𝐬𝐢𝐭𝐢𝐯𝐞 𝐜𝐚𝐬𝐞 𝐨𝐟 𝐄𝐇𝐕-𝟏/𝐄𝐇𝐌.

The National Finals Rodeo Committee released the following statement this morning in regards to the NFR event happening in December:
- “All horses must have a 7 day Certificate of Veterinary Inspection (CVI) and unique entry permit number obtained from the NV Dept. of Ag.
- All participants and competitors are responsible for daily temperature monitoring of their horses.
- There is a no-travel advisory for all horses participating and competing at the NFR.
- Enhanced verification and check-in procedures will be in place at the Thomas & Mack Center.
- Biosecurity measures will be maintained throughout the event.”

𝐓𝐡𝐞 𝐎𝐫𝐞𝐠𝐨𝐧 𝐃𝐞𝐩𝐚𝐫𝐭𝐦𝐞𝐧𝐭 𝐨𝐟 𝐀𝐠𝐫𝐢𝐜𝐮𝐥𝐭𝐮𝐫𝐞 (𝐎𝐃𝐀) has additionally released new rules to mitigate EHV risk. Exhibitions/events where other equines will be present need to register with the ODA at least 20 days prior to the event. Additionally, event organizers/producers need to have a record of all animals/competitors for 90 days following the event, which will only need to be made available to the ODA in the case of an outbreak. They recommend consulting with your licensed veterinarian on protocols to establish if a sick animal is discovered during the event, and a licensed veterinarian of record must be available to provide services during the event. If any animals show potential signs of infectious, contagious or communicable disease they will not be allowed entry to exhibitions/events, and should remain isolated until they are able to be examined by a veterinarian.

As this is an evolving situation, guidelines will likely continue to change. Please feel free to ask questions in the comments below.

Up to date information on reported positive cases can be found here: https://equinediseasecc.org/news/article/Equine-Herpesvirus-Myeloencephalopathy-(EHM)-Outbreak

Rules for the state of OR can be found here: https://www.oregon.gov/oda/animal-health-feeds-livestock-id/exhibitions/pages/exhibition-rules.aspx

-Dr. Cooper

11/20/2025