Equine Protozoal Myeloencephalitis (EPM) in Horses

Equine protozoal myeloencephalitis or EPM is a devastating neurological disease that can leave horses severely disabled and may result in death. EPM affects a horses central nervous system which includes the brain and the spinal cord. Symptoms may include abnormal gail involuntary muscle movements lethargy muscle atrophy and difficulty swallowing. Left untreated EPM will likely get progressively worse. Heres what horse owners need to know about equine protozoal myeloencephalitis.
What Is Equine Protozoal Myeloencephalitis?

Equine protozoal myeloencephalitis EPM is a neurological disease that affects the central nervous system of horses. The term myeloencephalitis means inflammation of the spinal cord and brain.
EPM occurs when a horse is infected with singlecelled microscopic organisms called protozoa usually the species Sarcocystis neurona. For reasons that are not well understood only a tiny percentage of horses exposed to S. neurona develop EPM. Although as many as 90 percent of the horses in some areas of North America test positive for exposure less than 1 percent develop the disease 1
Symptoms of EPM in Horses
The signs of EPM may resemble many other neurological diseases particularly in the beginning. This is a progressive disease meaning it tends to worsen over time. Some horses progress through the illness faster than others and its not uncommon for a horse to develop worsening symptoms then level off for a while sometimes even for months before once again beginning to deteriorate 1
Symptoms can vary depending on whether the horses brain or spinal cord is more heavily affected. But the following are common symptoms to watch for
Loss of coordination
Muscle atrophy
Difficulty swallowing
Behavioral changes
Standing with feet splayed or leaning against a wall for support
Weakness
Drooping eyelid
Head tilt
The symptoms of EPM can begin quite suddenly or slowly appear over time. As a general rule the signs are asymmetrical meaning they affect one side of the horses body more than the other 1 You might notice that your horse moves the legs on its left side in an uncoordinated fashion but still moves them normally on the right. The horse will often seem to have poor balance and may stumble or move abnormally. Its muscles might atrophy leading to weakness and further inability to walk normally
Spinal Cord vs. Brain
If the horses spinal cord is more affected which is the most common presentation of EPM youll notice more difficulties with movement balance and coordination. If the horses brain is more affected symptoms can include paralysis in the facial muscles making it difficult