Equine neuroaxonal dystrophy (NAD) is a degenerative central nervous system disease of horses. The disease is similar to equine degenerative myeloencephalopathy (EDM)
. NAD is thought to be inherited in Morgans, Appaloosas, and Quarter Horse breeds, which are the breeds most frequently affected. Clinical signs of NAD usually start to become apparent when horses are younger than 2 years of age.
Clinical Signs of NAD in Horses
Horses with NAD may initially appear depressed or dull, with weakness and mild to severe ataxia which appears as a gait abnormality. The gait abnormality affects all four limbs of the horse, however the hind limbs are most often the most severely affected. Horses with NAD may stand with a base-wide stance at rest.
Differences between NAD and EDM
NAD and EDM are both diseases that cause
degenerative changes in the central nervous system. The differences between them depend on the specific areas affected within the horse's central nervous system.
How NAD is Diagnosed
Diagnostic tests that are useful for determining whether a horse has NAD include a neurologic examination, radiographs (of the vertebrae of the neck), spinal tap, and measurement of vitamin E in the blood and diet. Your veterinarian will need to rule out other diseases which cause gait abnormalities, such as EDM, trauma, wobblers, and equine protozoal myeloencephalitis (EPM). A Postmortem exam is currently the only method to definitely diagnosis NAD or EDM.