Equine protozoal myeloencephalitis (EPM) is a parasitic infection of horses that can result in devastating neurologic disease. A small percentage of horses develop EPM after ingesting feed or water contaminated with Sarcocystis neurona, a one-celled protozoan organism.1 The pathogen is spread by opossums and carried by other animals. In a small percentage of clinical cases of EPM, a different protozoan called Neospora hughesi may also be responsible. In all cases, the disease attacks the central nervous system. 

Infection with S. neurona can also cause neuromuscular disease that does not result in destruction of neurological tissues, and this condition is more readily treatable. Diagnosis and treatment of EPM require that the veterinarian distinguish between EPM and non-brain associated S. neurona infections (sarcocystosis).2

Symptoms of EPM in the Horse

Since EPM is a disease of the central nervous system, it can affect multiple locations within the brain and spinal cord. Thus, the signs and severity of EPM can vary dramatically. While EPM can affect both the brain and spinal cord, it is more common for symptoms to be associated with damage to the spinal cord.1 

Many veterinary clinicians refer to “the 3 A’s” when cataloging symptoms of EPM: Asymmetry, Ataxia and Atrophy. 

• Asymmetry describes symptoms that are worse on one side of the body than on the opposite side. 

• Ataxia references incoordination or the inability of the horse to know exactly where its legs are.

• Atrophy is a condition where the muscles shrink from their normal size due to lack of use or neurological stimulation. 

Generally speaking, EPM has a poor prognosis if the parasites occupy the brain and spinal cord (CNS). In such cases, the damage is usually irreversible. That said, it has been noted that neuroinflammation from sarcocystosis often results in clinical signs that present similarly to EPM.2 In these cases, the parasite failed to migrate into the central nervous system, and the clinical signs were caused by the inflammation from the infection. 

Where to buy Diclazuril + Toltrazuril + Folic Acid Oral Paste 

Diclazuril + Toltrazuril + Folic Acid is typically available in the U.S. through veterinary custom compounding companies. 

Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

1Equus Magazine.

2aaep.org.

3UCDavis.edu.