EPM (Equine Protozoal Myeloencephalitis) is a moderately common neurological disease.
In the late 1980’s the parasitic organism was identified as Sarcocystis neurona and an antibody test was developed. Sarcoscystis falcutula has also been identified as potential cause of the condition and is less common.
Sarocystis neurona is now known to be present throughout the Western Hemisphere. The opossum has been determined to be a host within the cycle, with birds acting as intermediaries for the parasite. The incubation period for the disease is still unknown.
EPM affects different neurons throughout the neurological system and can result in dragging or spastic gaits. One side of the body may be affected, but not the other. If it affects the cranial nerves, the horse may have problems eating or drinking, have facial twisting, or undergo changes in the position of the eyes and ears.
Severely affected horses may become recumbent and have seizures.
Diagnosis of EPM is based upon finding antibodies or a DNA detection test from either blood or cerebrospinal fluid. There are still some challenges with accurate diagnosis.
A vaccine was developed, but has not been verified as effective at last report.
Biosecurity and Feed Security
It is very important to reduce the risk of horses consuming forage, water or feed that has been contaminated by opossums or any animals that may have consumed opossums.
Forage should be stored as securely as possible to minimize risk of contamination by fecal material and feeding management should be designed to reduce risk of contamination by opossums.
Pelleting and processing feed reduces/eliminates the risk of EPM transmission in feed or supplements. The feed should be securely stored in covered containers to prevent contamination on farm as contamination on the farm is a real risk.
To the degree possible, water sources should also be secure. A challenge with natural water sources!
Avoid having cat food or other food sources that attract opossums in the barn and stable areas.
Good biosecurity and sanitation are keys in reducing the risk of EPM for horses.