On the afternoon of November 18, 2025, the Office of the State Veterinarian, Arizona Department of Agriculture (AZDA) was notified by the Texas Animal Health Commission of several cases of Equine Herpes Myeloencephalopathy (EHM) involving horses that had competed at an event at Waco, Texas between 11/5-11/9 and two other subsequent events in Guthrie, OK and Stephenville, TX. Many of these horses have since dispersed back to their home states or have been hospitalized in adjacent states because referral hospitals have exceeded the capacity of their isolation stall facilities.

To date, no cases of equine neurologic disease associated with these recent shows have been reported in Arizona and veterinarians are lawfully required to report within 4 hours any confirmation of or suspicion of an EHM case. Unfortunately, the opportunity to quarantine febrile horses at those events in TX and OK 10 to14 days ago could not be leveraged so we must now mitigate risk to the best of our collective abilities.

The Office of the State Veterinarian is implementing the following movement restrictions effective November 20, 2025:

1. Interstate Certificates of Veterinary Inspection (ICVI), which would normally be valid for 30 days will now only be valid for 5 days if the origin state has had an EHM / Equine Herpes Virus-1 (EHV-1) detection in the previous 30 days. Those seeking to import horses into Arizona should consult with their State Animal Health Official (origin state) to determine if their state has confirmed cases or not.

2. Concurrently, all ICVI’s will also require the following supplemental statements:

a. The equids examined and represented on this certificate have no signs of respiratory disease, fever or any other clinical signs that may be consistent with EHV.

b. The equids referenced on this certificate do not originate from a facility currently subject to movement restrictions due to EHV investigation or that would be considered dangerous contacts to potentially exposed or infected horses within the previous 21 days.

3. All current Extended Equine Certificates of Veterinary Inspection (EECVI) are cancelled and EECVI availability will be paused for the next 30 days at which time the EHV situation will be re-evaluated. In the interim, ICVI’s needed for movement purposes will be required as described above for importation www.agriculture.az.gov into Arizona. For Arizona origin equine exports going to other states, please contact the respective destination State Animal Health Official for current import requirements.

To date, there have been no EHV detections or reports of sick horses in Arizona epidemiologically linked to the previously mentioned events in Waco and Stephenville, TX and Guthrie, OK. The Office of the State Veterinarian is not mandating cancellation of equine events currently. Out of an abundance of caution as we near the end of what would be the typical outside range of an incubation period (up to 14 days) following exposure at an equine event, the State Veterinarian would encourage a voluntary postponement and rescheduling of organized equine activities for an additional minimum of 2 weeks to provide that buffer while we wait to see if dangerous contact horses become symptomatic.

Should organizers be absolutely compelled to press on with holding events, the grounds biosecurity, risk mitigation, and contingency planning should include fully developed protocols for quarantine of horses that begin to display illness during the event. These protocols should define criteria that are being monitored by attendees (rectal temperatures twice daily on all horses >> fever if temperature is > 101.5 F) during the event for early detection of sick horses, and facilities to house these horses on-site in remote, open-air isolation stalls or temporary corrals placed to segregate these sick horses 120’ away from the general population. These horses should be fed, watered, and mucked last by dedicated people that do not handle similar duties in the general population without thorough disinfection. Above all, once these horses have been placed in isolation and the attending or show veterinarian has finished their evaluation, any suspicion of EHV-1 or EHM should be reported as soon as possible and no later than 4 hours after initial assessment to the Office of the State Veterinarian. The Arizona Department of Agriculture is currently working through attendee lists of the events in TX and OK, and will be reaching out to those individuals who have since returned to the state to ensure that proper risk mitigation, health monitoring, and dangerous contact quarantine protocols are enacted and reporting to the State Veterinarian is followed.

This isn’t the first time Arizona has had to deal with EHV-1/EHM risks, and it certainly won’t be the last time circumstances are thrust upon our state to deal with potential disease issues impactful to a significant portion of the equine sector. Most owners will prioritize the health and safety of their horses and those of other equine community members by making the right choices in avoiding unnecessary risk, to be responsible and compliant with state and event entry requirements, to maintain a robust herd health and wellness program in their stable, and to recognize when their horses are showing the subtlest signs of illness and take the initiative to scratch that event for long term success.