EPM stands for Equine Protozoal Myeloencephalitis and is a very serious disease that can occur in horses. Up to fifty percent of horses residing in the United States have had exposure to the organism that is responsible for EPM. This organ is a protozoal parasite that is called Sarcocystis neurona. The definitive host that spreads this disease is the opossum, and EPM is not transmitted between horses. The protozoa is received from birds with the infection.
Horses are exposed to sporacysts that are infected with Sarcocystis neurona while they are either drinking or eating water or feed that is contaminated (as a result of coming into contact with the birds that are infected). Once the horse has ingested the sporacysts, they move from the horse's intestinal tract into their bloodstream and finally into the blood/brain area. This is where the destruction and attack of the horse's nervous system commences. The disease can start off either slowly or rapidly and, if it is left untreated, can cause major neurological deterioration.
The symptoms of EMP disease can be varied and diverse. The signs are often asymmetrical, which mean they are different on both sides of the horse. Some symptoms include ataxia (lack of coordination), muscle atrophy, weakness, collapsing, seizures, narcolepsy, fatigue, muscle paralysis (eyes, face, mouth), having a hard time swallowing, lack of balance, head tilt, excessive sweating, stiff movements, loss of bodily and facial sensation and others.
There are certain factors that have potential influence of how slow or how fast EPM disease progresses. These factors are how long the horse houses the parasite before treatment starts, the number of sporocysts the horse ingested, and the location in the spinal cord or the brain where the organism settled and where the damage initially occurred.
Horses anywhere in the United States are at risk for contracting EPM disease. However, since the western area of the United States has a much lower opossum population, the incidence of EMP disease is markedly lower. EPM disease occurring is always much lower in areas without as many opossums.
There are several ways that you can help prevent horses from contracting EPM disease. Some things you can try include cleaning up any grains that might be dropped immediately to keep scavengers and birds at bay, making sure feed rooms and containers are always closed and sealed tightly, feed horses heated cereal grains (heating seems to kill the sporocysts), make sure to schedule plenty of frequent appointments with the equine veterinarian, making sure the horse's water tank is always clean and full of fresh, clean water and keeping your horse healthy with the proper nutrition, frequent exercise and vaccinations and deworming.