Over centuries, horses have been extensively bred for athletic characteristics, such as an ability to sprint short distances, pull heavy loads, or compete in endurance races. The intense selection for these performance traits has resulted in horses with enhanced muscle mass and improved physical performance. However, with the selection for these traits, reported muscle disorders have also become common. The surprisingly large number of known heritable muscle diseases in horses currently include polysaccharide storage myopathy type 1 (PSSM1), hyperkalemic periodic paralysis (HYPP), malignant hyperthermia (MH), immune-mediated myositis (IMM), PSSM type 2 (PSSM2), myofibrillar myopathy (MFM), and recurrent exertional rhabdomyolysis (RER) among others.
Disease-causing (mutant) alleles have now been identified for PSSM1, HYPP, MH, and IMM. These breakthroughs have presented researchers with the ability to genetically test for these alleles, determine if a particular allele is causing a disease in an individual horse, and determine an allele’s frequency in individual breeds. A private research company has developed, and is marketing, genetic tests that identify mutant alleles they have associated with PSSM2, MFM, and RER. However, the genetic mechanisms behind PSSM2, MFM, and RER are still widely unknown, and there is currently no public or published data demonstrating that these new alleles are associated with PSSM2, MFM, or RER in horses.
The UMN Equine Genetics and Genomics Laboratory is conducting a study that involves building a database of 3,000+ horses to: 1. conclusively determine whether the company’s proposed alleles are associated with PSSM2, MFM, or RER; 2. determine if these proposed alleles are influenced by environmental factors like diet and exercise; and 3. analyze any additive, interacting, or modifying effects these alleles have on each other, or their potential effects on clinical symptoms of other well-described muscle diseases like PSSM1, HYPP, MH, IMM, and more. Ultimately, the purpose of this study is to provide a deeper understanding of the genetic and management factors that influence muscle disease in horses and aid veterinarians, researchers, and horse owners in developing treatment strategies for muscle disease in individual horses.
We are requesting the help of horse owners to assist in this study by doing the following:
1. Provide information in our Muscle Disease in Horses Survey (tinyurl.com/rf5f8vp) for a horse on your property with suspected or diagnosed muscle disease.
2. Provide the same information in the same survey for another horse of similar age and breed on your property without suspected or diagnosed muscle disease.
3. Upload photos, videos, blood test results with creatine kinase (CK) and aspartate transaminase (AST) values, muscle biopsy results, and genetic testing results for each horse to our secure file-receiving folder on Dropbox.
4. Mail in hay, grain, supplement, and hair root or blood samples to our laboratory.
For more detailed instructions on how to participate, information about the study, and questions, please visit our website at tinyurl.com/qp29mll.
