Disorders of the Spinal Column and Cord in Horses

The bones of the spine and the nerves in the spinal cord can be affected by infection with bacteria, viruses, protozoa, or parasites. Sometimes the brain is also involved.

Bacterial infections include vertebral osteomyelitis, which is an infection of a spinal bone, and discospondylitis, which affects the cartilage discs that sit between the bones of the spine. These infections usually spread through the blood, and newborn foals are at the highest risk.

Viral infections, such as equine herpesvirus-1 and rabies, can also harm the spinal cord.

Equine herpesvirus-1 (EHV-1) can infect horses of any age but is more common in those older than 4 years. It damages small blood vessels in the central nervous system (CNS), leading to bleeding and damage to nerves. Signs often appear suddenly and can include dribbling urine, trouble passing manure, loss of feeling in the tail area, hind-end weakness, poor coordination, and sometimes paralysis (inability to move). There is no specific cure, but mild cases sometimes improve with nursing care (such as intravenous fluids, help with standing, protection from urine scald). Vaccination can help reduce EHV-1 infections (this vaccine is often referred to as the "rhinopneumonitis" vaccine, or "rhino" for short).

Rabies is a virus that causes severe inflammation of the brain and spinal cord. Rabies infection leads to worsening incoordination and paralysis and is always fatal in all animals and people. It can spread from horses to humans. See Rabies in Horses for more information. Vaccination is important for preventing rabies in horses, even though rabies is rare in horses.

Equine protozoal myeloencephalitis (EPM) is usually caused by a tiny infectious organism (a protozoon) spread by opossums. Signs can include weakness, poor coordination, partial paralysis, muscle loss, and sometimes problems with the nerves in the head. A veterinarian can diagnose EPM by noting the horse's symptoms, testing its CSF, and seeing how it responds to treatment. Many horses improve, but some have permanent nerve damage. Keeping opossums away from feed and water can help prevent EPM.

Certain parasites can enter a horse's CNS and cause sudden symptoms, often on one side of the body. These infections can be hard to diagnose, and recovery is not always complete. See Disorders of the Central Nervous System Caused by Parasites in Horses for more information.

Falls and other traumas can fracture or dislocate a horse's spine and injure its spinal cord. Swelling or bleeding can make the damage worse. It is possible for horses with mild injuries to recover with rest and pain medicine, but the outlook for horses that can't stand is poor.

For toxins that can affect the spinal column and cord in horses, see Peripheral Nerve Diseases Caused by Toxins.

Blood vessels (arteries, veins, and capillaries) carry blood throughout the body. Damage to blood vessels can also cause nerve damage. A rare but serious blood vessel problem in horses is postanesthetic hemorrhagic myelopathy, which can happen after general anesthesia, especially if a horse lies on its back for too long. Horses can become paralyzed after waking up, and the outlook is usually poor.

• Also see professional content regarding diseases of the spinal cord.