Equine Protozoal Myeloencephalitis - Symptoms

Symptoms

The neurologic signs that EPM causes are most commonly asymmetric incoordination (ataxia), weakness and spasticity, although they may mimic almost any neurologic disorder. Clinical signs among horses with EPM include a wide array of symptoms that may result from primary or secondary problems. Some of the signs cannot be distinguished from other problems, such as lameness, which can be attributed to many different causes. Airway abnormalities, such as laryngeal hemiplegia (paralyzed flaps), dorsal displacement of the soft palate (snoring), or airway noise of undetermined origin may result from protozoa infecting the nerves which innervate the throat. Apparent lameness, particularly atypical lameness or slight gait asymmetry of the rear limbs are commonly caused by EPM. Focal muscle atrophy, or even generalized muscle atrophy or loss of condition may result. Secondary signs also occur with neurologic disease. Upward fixation of the patella (locking up of the stifle joint) is among the most common findings among horses with neurologic disease. Another common side effect of EPM is back soreness, which can be severe. The actual method by which the Sarcocystis neurona infects a horse is still unknown, however it is thought to preferentially infect leukocytes (white blood cells) in order to cross the blood brain barrier.