With many horses being put out into spring time pastures, or grazing along trails, the scientists at Bayer Equine Connection are reminding horse owners about the potential for Equine Protozoal Myeloencephalitis which affects the horse's central nervous system.
EPM is a master of disguise. This serious disease can be difficult to diagnose because its signs often mimic other health problems in the horse and signs can range from mild to severe.
Grazing - One source of sporocysts
Over 50 percent of all horses in the United States may have been exposed to the organism that causes Equine Protozoal Myeloencephalitis.
More than 50 percent of all horses in the United States may have been exposed to the organism that causes EPM. The causative organism is a protozoal parasite named Sarcocystis neurona. The disease is not transmitted from horse to horse. Rather, the protozoa are spread by the definitive host the opossum. The infective stage of the organism, the sporocysts, are passed in the opossum's feces.
The horse comes into contact with the infective sporocysts while grazing or eating contaminated feed or drinking water. Once ingested, the sporocysts migrate from the intestinal tract into the bloodstream and cross the blood/brain barrier. There they begin to attack the horse's central nervous system. The onset of the disease may be slow or sudden. If left undiagnosed and untreated, EPM can cause devastating and lasting neurological damage.
The clinical signs of EPM can be quite varied. Clinical signs are almost always asymmetrical (not the same on both sides of the horse). Actual signs may depend on the severity and location of the lesions that develop in the brain, brain stem, or spinal cord.
Three things seem to influence progression of the disease:
- The extent of the infection caused by the number of organisms ingested
- How long the horse harbors the parasite prior to treatment
- The points in the brain or spinal cord where the organism localizes and damage occurs
If a horse shows signs of losing coordination, becomes sriff or stilted in its movements, has difficulty swallowing, abnormal sweating or is standing splay footed with drooping eyes, ears or lips, it has the symptoms that often indicate EPM, and a veterinarian should be called to make a diagnosis, and, if the horse does have EPM, to begin treatment,