Equine Motor Neuron Disease

Image of horses.

This relatively new disease was first diagnosed in 1990 in the state of New York. It’s still a rare condition and mostly confined to the United States.


Horse owners might first notice that their horse is eating plenty, but still managing to lose a lot of weight. He might have a short gait, anxious attitude and / or elevated heart rate. Here are some other symptoms:

  • Twitching muscles
  • All-over weakness
  • Sweating
  • “Camped under,” or tucked stance
  • Low head carriage and high tail carriage
  • Constant weight shifting and movement

The condition typically worsens over a period of one to three months, with occasional plateaus and even short spurts of improvement. Muscle atrophy sets in, and the horse becomes progressively debilitated.

Cause and Risk Factors

Researchers have not yet zeroed in on the cause of EMND. Many — but not all — horses with the disease are deficient in vitamin E. Quarter Horses and Thoroughbreds are more likely to develop EMND than other breeds, but this might be related to management practices.

Horses housed at one location for more than 18 months, and those with little or no pasture, form the majority of horses with EMND. These horses usually eat concentrate grain and grass hay.


Equine veterinarians diagnose horses with EMND using a combination of clinical signs and tests. A muscle biopsy taken from the tailhead will reveal characteristic lesions caused by specific motor nerves that have been damaged. Blood tests often reveal low levels of vitamin E and mildly elevated levels of two muscle enzymes in horses with EMND: aspartate aminotransferase and creatine kinase.


Horses with EMND need special care. If the disease is severe, encourage them to rest in deep bedding and provide green forage. Less severely affected horses should get access to a pasture. Talk to your equine veterinarian about adding a vitamin E supplement to your horse’s feed. For best absorption, buy natural, rather than synthetic, vitamin E.

The prognosis for horses with EMND is often grim. Many deteriorate so severely that equine veterinarians euthanize them within a month of the onset of symptoms. Others improve after moving to a new stable and taking vitamin supplements. Some survive but remain atrophied.

If your horse is showing any signs of EMND, call us today. For the best possible prognosis, immediate intervention is critical.


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