Prevalence of PSSM in Quarter Horses

Up to 6% of apparently healthy Quarter Horses could have subclinical polysaccharide storage myopathy (PSSM).
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Up to 6% of apparently healthy Quarter Horses could have subclinical (inapparent) polysaccharide storage myopathy (PSSM), and that percentage could be even higher in populations used specifically for breeding. Researchers at the University of Minnesota said that inadvertently breeding horses that have subclinical PSSM will perpetuate the disease in the Quarter Horse breed.

Polysaccharide storage myopathy is a common genetic cause of exertional rhabdomyolysis (tying-up) in Quarter Horses. Until now, researchers knew that 48% of Quarter Horses with signs of neuromuscular disease have PSSM, but they didn’t know how prevalent the disease was in apparently healthy breeding and performance Quarter Horses.

Molly McCue, DVM, MS, Dipl. ACVIM, and her colleagues took muscle biopsies from 164 apparently normal Quarter Horses on six ranches in six states, and she presented the study findings at the American College of Veterinary Internal Medicine’s Forum on June 1 in Louisville, Ky.

Five of the ranches that were primarily used for breeding and one performance horse ranch participated in the study. Two of the breeding ranches had previously produced PSSM horses. Those previously diagnosed horses were excluded from the study

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Written by:

Stephanie L. Church, Editorial Director, grew up riding and caring for her family’s horses in Central Virginia and received a B.A. in journalism and equestrian studies from Averett University. She joined The Horse in 1999 and has led the editorial team since 2010. A 4-H and Pony Club graduate, she enjoys dressage, eventing, and trail riding with her former graded-stakes-winning Thoroughbred gelding, It Happened Again (“Happy”). Stephanie and Happy are based in Lexington, Kentucky.

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