AIn a book I edited with Warwick Bayly, BVSc, PhD, Dipl. ACVIM, entitled Equine Internal Medicine (published by W.B. Saunders in 1998), there is a section on narcolepsy (page 454). In part, it reads: "Narcolepsy is a rare, incurable sleep disorder of the central nervous system characterized by uncontrolled episodes of loss of muscle tone (cataplexy) and sleep. The disease has been reported in Suffolk and Shetland foals (the fainting disease), Welsh ponies, a miniature horse, and in the Thoroughbred, Quarter Horse, Morgan, Appaloosa, and Standardbred breeds. A familial occurrence (heredity within a specific breeding line) is thought to exist in affected Suffolk and Shetland pony foals.

"Clinical signs of narcolepsy vary from mild muscle weakness to complete collapse. Adult horses may drop their heads, buckle at the knees, and stumble. If forced to walk, the horse may be ataxic (uncoordinated). Pony breeds are more likely to become recumbent. Horses and ponies that collapse may show absent spinal reflexes and REM sleep. Episodes may last from a few seconds to 10 minutes.

"The prognosis for narcolepsy is variable. Some newborn Thoroughbreds and miniature horses may have severe attacks, but recover fully. In Shetland and Suffolk ponies, the disease may persist throughout life, as is true with the adult-onset form