Prevalences and clinical signs of polysaccharide storage myopathy and shivers in Belgian draft horses

OBJECTIVE: To determine prevalences of polysaccharide storage myopathy (PSSM) and shivers in Belgian Draft Horses (BDHs) and determine whether there was an association between these 2 conditions. DESIGN: Prospective cohort study. ANIMALS: 103 BDHs > 1 year old. PROCEDURE: Owners were questioned regarding clinical signs of PSSM, shivers, and hindquarter weakness, defined as poor hindquarter muscling and lack of propulsion. Blood samples were collected for determination of serum creatine kinase and aspartate transferase activities and serum selenium and vitamin E concentrations. A biopsy sample from the gluteus medius muscle was submitted for histologic, histochemical, and biochemical analysis. A diagnosis of PSSM was made if abnormal amylase-resistant polysaccharide inclusions were seen histologically. RESULTS: 37 (36%) horses had PSSM and 19 (18%) had shivers, but only 6 (6%) had both PSSM and shivers, whereas 31 (30%) had PSSM alone, 13 (13%) had shivers alone, and 53 (51%) had neither, and a significant association between PSSM and shivers was not detected. Hindquarter weakness was found in 30 horses. Only 13 of 37 (35%) horses with PSSM and 11 of 19 (58%) horses with shivers had hindquarter weakness. Serum creatine kinase and aspartate transferase activities and serum selenium and vitamin E concentrations were not significantly different between horses with and without PSSM or between horses with and without shivers. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that PSSM and shivers are common but unrelated disorders in BDHs.