Equine Motor Neuron Disease in a Knabstrupper Horse

ABSTRACT
A case of equine motor neuron disease (EMND) is described in a twelve-year-old, Knabstrupper gelding with a three-month history of fatigue and weight loss. Shivering, increased sweating, weight-shifting, muscle fasciculations, base-narrow stance, excessive recumbency and gluteal muscle atrophy were also observed. Serum vitamin E and selenium levels were found to be below normal. A sample from the gluteus medius muscle was obtained by open biopsy. The muscle appeared to be relatively normal with the routine stains. ATPase reaction showed type I and type IIA atrophy and excessive fibre size variation in type I, IIA and IIX fibres. A diagnosis of EMND was made based on clinical signs, laboratory findings, history of poor access to green forage and muscle biopsy. The horse was treated with vitamin E/selenium oral supplements. A significant improvement was observed by the owner in the following months, but muscle atrophy was still noticeable. Due to the the sporadic occurrence of EMND, many of clinical signs associated with the condition are non-specific, therefore this case demonstrates that the described clinical signs warrant consideration of EMND as a possible cause, and it is useful for clinicians to be aware of this. While EMND has been diagnosed in several breeds, espeically in Quarter horses and Thoroughbreds, this case is the first report of this condition in Knabstrupper horses. Most useful diagnostic tests included determination of vitamin E concentration in serum and muscle biopsy. Besides, our findings we confirm the feasibility of diagnosing EMND by means of gluteus medius muscle biopsy.

Keywords: Horse; Motor Neuron Disease; Knabstrupper; Muscle Biopsy.
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