Equine Protozoal Myeloencephalitis (EPM)

Equine Protozoal Myeloencephalitis (EPM) is a disease contracted by the microbe, Sarcocystis neurona typically found in opossum feces, that can cause neurologic disease due to the effects of the microbe to the brain and spinal cord. The microbe can also be carried by domestic cats, skunks, and armadillos, which can be directly transmitted to horses unlike in the opossum. 

Signs of EPM can resemble other neurologic diseases, and can be irregular in that signs may go away over time and later reappear. Signs can include incoordination, which can be exhibited more vividly when the horse’s head is up and the horse is moving forward, or when moving up or down hills. EPM may also show itself by an irregular gait exhibited in the horse; stiffness; muscle atrophy; drooping lips, eyes, or ears; unusual sweating; seizures; and loss of sensation in the body, neck or face of the horse. 

A serum antibody blood test can be used to detect if any Sarcocystis neurona antibodies are present, which would mean the horse has been exposed to the microbe at some point in life. However, the presence of antibodies does not mean that the horse has the disease. A 28-day treatment of antiprotozoal (ponazuril), the only FDA approved treatment for EPM, can be prescribed. In some instances, horses may require a second 28-day course of ponazuril for treatment. 

Beginning treatment early will lead to more favorable results. Approximately 60 to 70 percent of horses improve following treatment for EPM, and roughly 15 to 25 percent of horses recover. 

To help prevent EPM in horses, keep feed in closed containers to prevent animals from accessing. Ensure facilities are clean as cluttered environments can be welcoming to animals. Ensure wildlife does not have access to barns by blocking entrances, and check for indications of wildlife such as feces and chewed material in barns and in feed rooms. Garbage and food for cats and dogs should be secured as well. Cats and dogs should also be fed away from where horses eat and away from where feed is stored.

Consult with your equine veterinarian if you think your horse may be exhibiting signs of EPM.

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