Equine protozoal myeloencephalitis (EPM) is a central nervous system (CNS) infection of horses with either of the apicomplexan protozoa Sarcocystis neurona or Neospora hughesi.1 EPM is a common neurologic disease of horses that occurs only in the Americas. EPM has been reported in most of the contiguous 48 states of the USA, southern Canada, Mexico, and several countries in Central and South America.  

Most cases of EPM are caused by the S. neurona protozoan. Horses become infected by ingesting the S. neurona sporocysts in contaminated feed, grass (while grazing) or water. The definitive host for S. neurona in North America is the opossum (Didelphis virginiana). These animals are notorious for eating or scavenging just about anything, and typically become infected by eating sarcocyst-containing muscle tissue from an infected intermediate host. Thereafter, infectious sporocysts are passed in the opossum’s feces. 

EPM is an extremely serious disease that can cause devastating and lasting neurological damage in the horse and can ultimately prove fatal. It is also very common. In some areas of the U.S., over 90% of horses can be seropositive, meaning that they have been exposed to the S. neurona sporocysts. Horses with antibodies specific to N. hughesi have been found in 21 states and, in some locations, up to 20% of horses may be seropositive to this organism.2  Fortunately, most horses are able to mount a sufficient immunological defense and only a very small percentage of horses seropositive to either parasite (around 1%) will develop clinical disease. EPM can also be difficult to diagnose because its signs often mimic other health problems in the horse and can range from mild to severe.

EPM: Clinical Signs

Common clinical signs of EPM include:

• Ataxia (poor coordination)

• Spasticity (stiff movements) 

• Abnormal gait

• Lameness

• Muscle weakness, particularly under exertion

• Muscle atrophy along the topline, or in muscles of the hindquarters

• Facial paralysis

• Difficulty swallowing

• Seizures

• Collapse

• Abnormal sweating.

• Head tilt

• Poor balance

• Leaning against stationary objects

Treatment of EPM in Horses

Any horse suspected of displaying clinical signs of EPM should be seen by an equine veterinarian immediately. EPM is treated with antiprotozoal drugs and immunomodulators.3 

NOTE: The Association of Racing Commissioners International Uniform Classification Guidelines for Foreign Substances has designated levamisole a CLASS 2 DRUG.

Where to buy Diclazuril + Levamisole 

Diclazuril + Levamisole is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. 

This product carries several potential drug interactions. 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.

1Merck Veterinary Manual.

2Reed, S M et al. Equine Protozoal Myeloencephalitis: An Updated Consensus Statement with a Focus on Parasite Biology, Diagnosis, Treatment, and Prevention. Journal of veterinary internal medicine vol. 30,2 (2016): 491-502. doi:10.1111/jvim.13834.

3Dubey, J.P. et. al. (2001). A review of Sarcocystis neurona and equine protozoal myeloencephalitis (EPM). Veterinary parasitology. 95. 89-131. 10.1016/S0304-4017(00)00384-8.