Aleman said vets at UC Davis have found large numbers of S. fayeri parasites in the skeletal muscle of diseased horses, and there are also anecdotal reports of horses with lameness and stiffness (but no characteristic signs of incoordination or muscle wasting) responding to treatment with antiprotozoal drugs. | Photo: The Horse Staff

Historically, veterinarians have reported finding parasites in the skeletal muscle of some horses with neuromuscular disease. One they’ve always written off as an incidental finding or not actually related to the neuromuscular disorder, is the protozoan parasite Sarcocystis fayeri.

Monica Aleman, MVZ, PhD, Dipl. ACVIM, an associate professor of medicine and epidemiology at the University of California, Davis (UC Davis), School of Veterinary Medicine, believes, however, that there’s more to it. She studied S. fayeri’s prevalence in horses with neuromuscular disease and presented her results at the 2018 American Association of Equine Practitioners Convention, held Dec. 1-5 in San Francisco, California.

“At UC Davis we’ve found large numbers of S. fayeri in the skeletal muscle of diseased horses,” she said. “There are also anecdotal reports of horses with lameness and stiffness (but no characteristic signs of incoordination or muscle wasting) responding to treatment with antiprotozoal drugs