Decoquinate Combined with Levamisole Reduce the Clinical Signs and Serum SAG 1, 5, 6 Antibodies in Horses with Suspected Equine Protozoal Myeloencephalitis

Sarcocystis neurona is an apicomplexan parasite that can cause mortality in domestic and wild animals. It is an important cause of the neurological disease equine protozoal myeloencephalitis (EPM) in the Americas. Different surface antigen (SAG) phenotypes have been observed for S. neurona, and not all isolates of S. neurona contain the genes (SnSAG) to encode all SAGs. Recent studies indicate the presence of antibodies to the antigens SAG 1 and SAG 5 are present in most cases of clinical disease. Using sera from horses with a presumptive diagnosis of EPM, we examined 141 horses for antibodies to disease-associated SAG phenotypes of S. neurona using an indirect ELISA employing recombinant SAG’s 1, 5, and 6 as antigens. An immunochromatic Sarcocystis neurona multiplex antibody detection kit (Centaur, Olathe, KS.) was evaluated for the rapid detection of antibodies to SAG 1, 5, and 6 of S. neurona. One hundred fortyone horses with a presumptive diagnosis of EPM were treated with a combination of decoquinate (0.5 mg/kg) and levamisole (1 mg/kg) in an oral paste, Oroquin-10 (Francks Compounding Labs, Ocala, Fl.), for 10 days and monitored for a treatment response. Successful treatment of EPM was determined by a reduction in clinical signs by clinical neurological examination and a reduction in antibodies 4-6 weeks post treatment. A reduction in clinical signs was seen in 132 (93.6%) horses and reduced antibody titers were observed in 126 (89.3%) horses. The detection of antibody against recombinant SAG’s 1, 5, 6, and a response to decoquinate/ levamisole identified horses with clinical EPM. The rapid detection of SAG phenotype using the multiplex antibody detection kit facilitated identification of significant antibodies and evaluation of a