Common Neurological Disorders Defined
Disorders of the horse’s central nervous system fall into multiple categories. These include (but aren’t limited to) degenerative, nutritional, metabolic, immune-mediated, toxic and infectious. “In adult horses, the most common categories would be degenerative [arthritis], anatomic and infectious,” says Dr. Johnson. The latter category includes viral, bacterial and parasitic causes, she adds.
Here’s an overview of the causes, preventions and treatments for the diseases discussed. For information on diagnosing these disorders, see pages 60–62.
Equine Protozoal Myeloencephalitis
Cause: Horses become infected by consuming food or water contaminated with opossum feces containing the parasite Sarcocystis neurona, which then moves into the horse’s central nervous system. Horses under 5 and over 13 may be at higher risk. Anything that compromises your horse’s immune system can also increase risk.
Prevention: Minimize your horse’s exposure to opossum feces. In areas with opossum populations, avoid feeding your horse off the ground and keep feed stored away safely.
Treatment: There are three FDA-approved medications to fight S. neurona— ponazuril, diclazuril and sulfadiazine used in combination with pyrimethamine. Some vets may also recommend a vitamin E supplement.
Eastern and Western Equine Encephalomyelitis and West Nile Virus
Cause: These viral diseases are spread by infected mosquitoes with the virus attacking the horse’s central nervous system. WEE is seen in western North America and as far south as Argentina. EEE has appeared in every U.S. state east of the Mississippi as well as a few other states. West Nile virus is prevalent over the entire U.S.
Prevention: Vaccinate your horse as recommended by your veterinarian and practice good mosquito mitigation.
Treatment: There is no treatment for these diseases. Your vet can provide supportive therapy—for instance, treating a fever, providing intravenous fluids and nutrition and treating any secondary infections.
Cause: This viral disease is spread by direct horse-to-horse contact or with a contaminated object, such as buckets, clothing or skin that have been in contact with an infected horse. While many horses are exposed to the disease early in life, the virus can be inactive for years and appear during times of stress, like long-distance trans-
port or strenuous exercise.
Prevention: Vaccinate. “The vaccination does not protect the horse from the neurologic form of the disease,” says Dr. Johnson. “However, it might help reduce viral spread during an outbreak, leading to fewer affected horses.” Be cautious of allowing your horse to have contact with other horses or communal water troughs at shows and other places where horses from different locations gather.
Treatment: Supportive care. Antiviral drugs might help prevent disease or limit its effects, says Dr. Johnson. Treatment for secondary concerns might also be warranted, such as antiinflammatories or antibiotics.
(Also known as cervical vertebral stenotic myelopathy or cervical vertebral malformation)
Causes: Wobblers affects the horse’s neck and may be caused by bone malformation, malarticulation, developmental bone disease or arthritis. The common result is that the vertebrae press against the spinal cord, causing compression that can interfere with nerve messages traveling from the brain to the limbs.
Prevention: None. “Breeding horses known to have wobblers is not recommended,” notes Dr. Johnson. “Pushing young horses for rapid growth might contribute to disease in genetically predisposed individuals.”
Treatment: Depending on the cause, treatment includes surgery, antiinflammatory medication, physiotherapy, stall rest or nutritional changes.
Many common neurological diseases can be prevented through the use of certain vaccines, as recommended by your vet.