Bronson, DVM: EMND

By Dr. Joanna Bronson | http://bronsonvetservices.com/

Equine motor neuron disease was first recognized in the Northeastern part of the United States, but cases are now found all across the U.S. and in Canada, Europe, the British Isles, Japan, as well as Brazil.

This disease (EMND) typically occurs in older horses that have been Vitamin E deficient for more than 18 months. Vitamin E is a necessary element that functions as a biological antioxidant helping maintain normal neuromuscular functions.

EMND affects lower motor neurons interfering with neurological input into the muscles. Certain horses are more susceptible to developing neuron diseases and a deficiency in vitamin E plays a significant role in the development of EMND in those individual horses. However, not every horse who is vitamin E deficient will develop this disease.

Signs of a suspected case of EMND are obvious.

Affected horses will display muscle atrophy, weakness, and weight loss even with a normal or increased appetite. Weight loss can be as much as 200-300 pounds, even if the horse has a good appetite. This weight loss is due to the degenerative atrophy associated with motor neuron disease. Weight loss usually shows up before any other clinical signs.

This disease usually affects older horses with the peak age for risk beginning around age 16. However, the onset of this disease can start as early as 15 months of age. Both genders are susceptible to EMND, and there has been increased documentation of susceptibility in certain breeds including standardbreds, quarter horses, and thoroughbreds.

Besides a noticeable weight loss, other clinical signs may include muscle twitching and sweating. An affected horse may also carry his head lower than normal, want to lie down for longer periods of time, and will appear uncomfortable standing. When lying down, EMND will cause him to want to rest his chin on the ground to support the weight of his head and neck.

An affected horse may also stand with his pelvic limbs braced under his abdomen, or he may frequently shift his weight, as he will be unable to “lock his stifles” to help support his weight. With movement, he may occasionally stumble and display a shortened or “string-halt” stride displaying an elevated tail head. Many affected horses do feel better in motion compared to when standing still. When diagnosing and ruling out other spinal problems, the horse's desire to move instead of wanting to stand still is a guide for suspecting EMND.

Horses with EMND will also often appear hyperalert and will display worried facial expressions.

To determine a positive diagnosis, EMND is identified based on a horse's history, clinical signs, and laboratory findings including a muscle biopsy taken from the tail head. This test will reveal histopathologic evidence of damage to the neurons. A blood test can determine a baseline vitamin E level and should be repeated regularly to see if the levels need adjustment. Affected horses are treated by adding or changing the vitamin E level in their diets. Vitamin E is most often fed in combination with the mineral Selenium which is also essential for good health. With treatment, approximately 40% of affected horses improve, 40% stabilize, and 20% progress in the severity of the disease. Many areas of the United States are known for producing selenium deficient forage including parts of the Pacific Northwest, the Great Lakes, and down the Eastern Seaboard into Florida. In these areas, selenium supplementation is a necessity.

The minerals Selenium and vitamin E allow the body to protect the cells from oxidative damage by fortifying the body's immune system. Vitamin E is essential for proper functioning of many systems including reproduction, muscle development and function, and the nervous, circulatory, and immune systems.

Vitamin E must be obtained through a horse's diet. Calculating how much vitamin E to feed is determined by body weight, physiological status, and required level of work. Supplementation is especially warranted for horses who are not consuming pasture year-round, are undergoing moderate to heavy exercise, are growing, or are lactating. Although a horse may be on pasture, he can still develop a vitamin E deficiency. It is important to address a horse's whole diet to ensure he is receiving a balanced diet which meets his individual nutritional requirements. If the horse will respond to therapy, it usually takes a minimum of 3 to 6 weeks for observable improvement to be noticed. The ideal prevention for EMND is feeding quality forage (pasture or hay), grain when needed, and supplementing for recognized vitamin and mineral deficiencies in the diet. Dr. Joanna Bronson graduated from MSU College of Veterinary Medicine in 2000 at the top of her class. Following graduation, she worked as an intern at a large equine referral practice in Cleveland, OH, specializing in lameness, surgery, and racetrack medicine. In 2005, she opened Bronson Veterinary Services in Coldwater, MI. What started as an ambulatory only practice, quickly grew to a fullservice equine and small animal hospital and surgical center. The now three doctor practice provides medical, surgical, reproductive, and preventative care services for Branch County and the surrounding area. Dr. Bronson is committed to promoting responsible pet ownership, preventative healthcare and health-related educational opportunities for her clients. Her practice offers a number of resources to learn about how to take better care of your pets. For more information please visit www.bronsonvetservices.com