In February, Oklahoma experienced its first ever equine herpesvirus myeloencephalopathy diagnosis, and it happened here in our hometown. OSU’s Center for Veterinary Health Sciences released a public statement on February 13 reporting a confirmed case of EHM in their care. The equine barn was temporarily closed in order to quarantine the horse. When I first read this press release I immediately felt anxious about the horses in my barns, and maybe you did, too. Or perhaps your memory went back to 2011 when, in Ogden, Utah, a number of cutting horses were diagnosed with EHV-1 and ultimately affected a total of 90 horses in ten different states. According to the Animal and Plant Health Inspection Service, 13 of these horses died or were euthanized. This was not an easily forgotten event for horse owners across the country.
It’s easy to get scared and act irrationally when things like this happen, but I’m hoping to dispel some of those fears and replace them with a bank of knowledge and preparedness. On Tuesday, February 24, the Center for Veterinary Health Sciences held a public meeting to address any questions horse owners might have about the disease. Dr. Todd Holbrook, along with a panel of other invested veterinarians, including our state veterinarian, Dr. Rod Hall, presided over the meeting and took great effort to present the audience with all their available information. Here are a few important facts about EHM they discussed:
• Equine herpesvirus type 1, or EHV-1, produces respiratory disease, late gestational abortion in mares, or even the neurologic mutant strain equine herpesvirus myeloencephalopathy, known as EHM.
• EHV-1 is found worldwide. Of the two strains, 80-90% of cases are EHV-1, while only 10-20% of cases result in the neurologic form of EHM.
• About 80% of the equine population has already been exposed to EHV-1 at some point in their lives.
• Thus, the virus can live inactively in the lymph nodes until the horse becomes stressed by traveling, showing, trailering, etc. and the virus begins to actively shed. In some cases, the virus can be presented in the neurologic form, or EHM, which is what was diagnosed at OSU.
• Symptoms of EHV-1 include nasal discharge, fever, and coughing. EHM can also produce these symptoms, but will also show limb edema, ataxia usually in the hind limbs, urine dribbling, and loss of tail tone. In worse cases, the horse may not be able to stand on its own.
So how can we protect the animals we love from this disease? Dr. Holbrook spoke on the importance of quarantining new horses or horses who are returning from shows, if at all possible. Respiratory transmission is the most common way the disease spreads. Isolate and carefully watch these horses for symptoms. The incubation time for EHV-1 is one to two days before a horse generally shows symptoms, while the incubation time for EHM is closer to eight to 12 days. Broodmares should be housed separately from geldings and show horses, in order to protect against abortion. Disinfect water buckets, feed pans, and tack regularly. Lastly, vaccinate your horses. While there is no vaccination for EHM, it is still crucial to vaccinate for EHV-1. Horses who travel regularly can be vaccinated up to three times a year, Holbrook said.
Knowledge is power. Knowing how to protect your horse and understanding the disease is the first step to confidently preventing the disease on your own property. I am not a veterinarian, nor an expert on this subject, but I hope what I have learned from Dr. Holbrook and his team at OSU will help you as much as it did me. I encourage you, as horse owners, to educate yourself and do your own research as well.