Estimated prevalence of polysaccharide storage myopathy among overtly healthy Quarter Horses in the United States.

The research aimed to determine the prevalence of Polysaccharide Storage Myopathy (PSSM) among healthy Quarter Horses in the United States and analyze its relationship to muscle glycogen concentration, turnout time, and exercise level. The findings show that the prevalence of PSSM among Quarter Horses is likely to be between 6% to 12%.

Study Details

• The study was cross-sectional in design and involved 164 overtly healthy Quarter Horses that were over two years old, taken from 5 states in the United States.
• Horses with a history of exertional rhabdomyolosis or any other muscular disease were excluded from the study.
• Muscle biopsy specimens were examined histologically for evidence of PSSM and were submitted for the determination of muscle glycogen concentration.
• A diagnosis of PSSM was made if amylase-resistant inclusions that stained with periodic acid-Schiff stain were detected.

Results

• On two farms that had a history of PSSM, the prevalences were 20% (1 out of 5 horses) and 40.7% (11 out of 27 horses) respectively.
• The mean prevalence for the other four farms was calculated to be 6.1% (8 out of 132 horses).
• The sex of the horses was not significantly associated with a diagnosis of PSSM, and the age did not differ significantly between horses with and without PSSM.
• Total histologic score, serum creatine kinase activity, and muscle glycogen concentration were found to be significantly higher in horses with PSSM than in horses without it.

Conclusion

• The study’s results suggest that the prevalence of PSSM among otherwise healthy Quarter Horses in the United States could be between 6% and 12%.