Pathogenes Inc.

Equine Protozoal Myeloencephalitis is a preventable disease. 

There is a difference between EPM and sarcocystosis.  Sarcocystosis is an infection with a Sarcocystis organism.  It is an infection that is limited to the gut or organs outside the CNS.  Horses can be infected by 3 different Sarcocystis.  EPM is a disease, myelo-encephalitis, with parasites in the brain or spinal cord and the horse is ataxic.  Only S. neurona can do that, and not all neurona's cross into the CNS.

Sarcocystis infections in horses are caused by ingesting oocysts from the environment.  The oocysts in the gut release infectious parasites that use the blood stream spreading to organs (infections) and sometimes the central nervous system (EPM).  Sarcocysts are members of the Coccidia.

Coccidia is a subclass of microscopic, spore-forming, single-celled obligate parasites belonging to the apicomplexan class Conoidasida. Coccidian parasites infect the intestinal tracts of animals, and are the largest group of apicomplexan protozoa.

Coccidia are obligate intracellular parasites.  That means they must live and reproduce within an animal cell.  Coccidiosis can be prevented in animals and horses can be protected as well. 

Protecting against EPM

The best protection is through induced immunity. We  showed that vaccination with SnSAG 1 can protect against homologous challenge.  The vaccine protected animals against signs of EPM by producing antibodies that attack the blood stage of the parasite.  We protected horses against EPM. 

The most common method used to prevent coccidia in farm animals is by using medications that attack the organism in the gut before parasites enter the blood stream.  Until a vaccine becomes available preventing disease using medications in horses is necessary.  High risk horses that are in environments with high exposure or experience relapse or chronic relapsing disease benefit from prevention therapy.