EPM has always been described as a disease of protozoa in the CNS. The protozoa cause lessions in the CNS when they reproduce. The lessions interfere with nerve signals, and the horse has limited feeling and awareness of the limbs (or face, jaw, tail). It has been known for years that inflammation of the CNS plays a large part in lessions and nerve damage. Anti-inflammatories have always played a part in the treatment for EPM.
What if, inflammation plays a much larger role than was previously recognized? Inflammation may be caused by the toxins produced by Sarcocystis neurona, but what if long, drawn-out EPM symptoms are a manifestation of inflammation, not the protozoa?
Researcher Siobhan Ellison, DVM is looking into this question. See the November 29th blog here: Pathogenes Research Blog.