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EquiSearch’s Ask the Vet: Horse Seizures

Dr. Joyce Harman explains what can cause seizures in horses and how to handle them in this edition of's Ask the Vet.

Photo by Cappy Jackson
It is possible, though very uncommon, for vaccines to trigger seizures.
Photo by Cappy Jackson

Question: The other day my husband's horse was acting strange. I was cleaning the barn, and she was tied up and when I went to get her she had stiffened up just like my old dog does when he's about to have a seizure. Do horses have seizures? Or could it have been a mini-stroke?

Answer: Yes, horses can have seizures, though it is not too common. A single seizure may not be a problem, but if there is a second one you should have your veterinarian examine him. Seizures in horses can be very dangerous if you or any family member is near him when it happens. The causes can be Equine Protozoal Myelitis (EPM), tetanus or rabies, as well as viral or fungal infections. Tumors are not uncommon in older horses, and chemical toxins can trigger seizures at any age. Head trauma is likely the most common origin of seizure in the equine. It is possible to trigger a seizure with a vaccination also.

Think back to anything in the recent history of your horse. Has she had any drugs or vaccines? Has there been any change in feed, hay or pasture? Did you see a small cut or scrape on her head or near her ears? Is she as coordinated when you are riding her or has she started to stumble a little? Has she or any other horse on the farm had a runny nose recently?


If this is an ongoing problem you and your veterinarian will need to discuss diagnosis and treatment options. Certainly a good neurologic exam, perhaps at a university, a blood chemistry test and possibly head X-rays are helpful to see if there are any obvious problems. An MRI that can look at the brain for a tumor can be done if that is available in your area. An EEG can also be done to test the brain function.

For treatment, the drugs used for seizures are not well researched in horses and can be expensive. They also may work for a while but could stop working without warning, so everyone handling her must be aware of the possibility that another seizure could occur. If there is no tumor, it is also possible to treat some of the these cases with Chinese Herbal Medicine, if you have a practitioner near you. Check Alternative Healthcare Organization Links for help finding a practitioner. Good luck with your horse and, above all, be careful until you are certain what is going on.

Dr. Joyce Harman is a veterinarian and respected saddle-fitting expert certified in veterinary acupuncture and veterinary chiropractic; she is also trained in homeopathy and herbal medicine. Her Harmany Equine Clinic is in northern Virginia. Visit her online shop.

Have you had a similar experience? Chat about it in the Forum.

Do you have a veterinary question for Dr. Harman? Send it to Check back for her answers on

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