Serum Antibodies Against a Reactive Site of Equine Myelin Protein 2 Linked to Polyneuritis Equi Found in Horses Diagnosed with EPM

Equine protozoal myeloencephalitis (EPM) is the most commonly diagnosed infectious neuro-degenerative condition in horses and neuroinflammation is present in all definitively diagnosed cases. Historically EPM is difficult to treat. Polyneuritis equi (cauda equina neuritis) is a rarely recognized noninfectious, chronic relapsing, peripheral neurodegenerative disorder in horses. We propose that polyneuritis equi may be associated with Sarcocystis neurona infections because we demonstrate the presence of antibodies against equine myelin protein and S neurona surface antigens in 78% (n=55) of serum from ataxic horses with a presumptive diagnosis of EPM. Serum antibodies against S neurona were detected in a horse with histopathologically confirmed immune mediated polymyositis and intramyofiber sarcocysts. INTRODUCTION Equine protozoal myeloencephalitis (EPM) is the most commonly diagnosed infectious neuro-degenerative in horses. Little attention has been paid to the inflammatory component of disease despite the presence of neuroinflammation all definitively diagnosed cases of EPM. Histopathologic examination of a horse with EPM overwhelmingly reveals central nervous system (CNS) inflammation without the associated CNS presence of protozoa. It remains dogma that the clinical signs of EPM are due to presence of parasites in the CNS, and that the area of parasitization determines the signs observed .1 It is more likely that clinical signs of EPM are due to a combination of parasitization and inflammation. Peripheral polyneuritis (polyneuritis equi) causes signs similar to EPM and is a rarely recognized, auto-immune, chronic relapsing, disorder in horses. We associate polyneuritis equi with Sarcocystis neurona infections by demonstrating the presence of serum antibodies against myelin proteins and S neurona surface anSerum Antibodies Against a Reactive Site of Equine Myelin Protein 2 Linked to Polyneuritis Equi Found in Horses Diagnosed with EPM Siobhan P. Ellison, Pathogenes Inc. Tom Kennedy, Eleven Bravo Inc. Austin Li, Senior Scientist, Pathogenes Inc. Lark Schweiss, Pathogenes Inc. Corresponding Author: Siobhan P. Ellison DVM PhD 15471 NW 112 Avenue, Reddick, FL 32686 Phone: 352-591-3221 Fax: 352-591-4318 e-mail: [email protected]