Miniature Horses and Equine Narcolepsy
A disorder not often found in horses, seems to be more common in the smallest breed, the Miniature Horse. Miniature owners refer to the little horses with the disorder as "fainting foals." People are probably more familiar with fainting goats, and even humans can have the disorder. Yet, the disorder has been reported in several light horse breeds and pony breeds. Narcolepsy is more common in foals, and they do normally out-grow it as they age. A survey of Miniature Horse Breeders done by the University of Wisconsin showed narcolepsy to be a "rare but distinct syndrome in the Miniature Horse."
Narcolepsy involves a chemical imbalance in the brain cells that control sleep and wakefulness. The symptoms can vary from a mild muscle weakness to full collapse. Usually the horse is at rest when the episode happens. Narcolepsy seldom occurs while the horse is being worked. The horse behaves as though it has been tranquilized, and will stagger if asked to move.
Equine veterinarian, Dr. Douglas Novick, explains in an article titled "Narcolepsy - the Sleeping Disease" that the disease is a biochemical abnormality believed to be in the sleep-wake center of the brain. He writes, "One of three neurotransmitters (chemicals in the nervous system that pass information from one cell to the next), serotonin, dopamine, and norepinephrine may be responsible for the problem."
The episodes don't last long, maybe up to ten seconds, but there is always the danger the horse will injure itself or its handler in a fall when it collapses. Narcolepsy can be very frightening to witness.
A test is available to diagnose narcolepsy. A drug is administered to the horse and if the animal has narcolepsy it will have an episode within minutes. The narcoleptic horse can be treated with the anti-depressant Imipramine, which suppresses REM sleep. When a horse exhibits symptoms of narcolepsy, a veterinarian should be consulted, especially since the symptoms could be caused by a number of other diseases or conditions including EPM and epileptic seizures.