It is a relatively new condition, first diagnosed in 1990 in New York state, that affects the nervous and muscular systems in adult horses. To date, less than 100 horses have been diagnosed with this illness.
Affected horses demonstrate marked weight loss in the face of a ravenous appetite.
This weight loss is attributed to neurogenic muscular atrophy. Presently there is no know cause of the disease. Other signs may include constant shifting of weight in the rear limbs, and abnormally low head carriage. The condition usually progresses with continued muscle atrophy and debilitation over the course of one to several months. Occasionally the condition will stabilize or even seem to improve one to two months after the onset.