Prevalence of clinical signs and factors impacting expression of myosin heavy chain myopathy in Quarter Horse-related breeds with the MYH1E321G mutation.
Abstract: The prevalence of clinical signs and factors triggering muscle atrophy and rhabdomyolysis associated with an MYH1 mutation in Quarter Horses and related breeds (QH) remain poorly understood. Objective: Determine the prevalence and potential triggers of atrophy and stiffness in horses homozygous reference (N/N), heterozygous (My/N), and homozygous (My/My) for the MYH1 mutation. Methods: Two-hundred seventy-five N/N, 100 My/N, and 10 My/My QH. Methods: A retrospective case-control study using a closed-ended questionnaire completed by clients of the Veterinary Genetics Laboratory at the University of California, Davis. History of clinical signs, disease, vaccination and performance were analyzed by genotype using contingency testing. Results: Atrophy occurred in proportionately more horses with MYH1 (My) than N/N QH and more frequently in My/My than My/N QH (P < .001; My/My 8/10 [80%], My/N 17/100 [17%], N/N 29/275 [11%]). More My/My horses had rapid atrophy (P < .001), with recurrence in 50%. Fewer My/My horses recovered versus My/N QH (P < .001). Stiffness was common across genotypes (P = .100; My/My 4/10 [40%], My/N 18/100 [18%], N/N 48/275 [17%]). Three months before the observed atrophy and stiffness, 47% of MYH1 QH were vaccinated or had respiratory or gastrointestinal disease. Horses achieving 100% expected performance did not differ across genotypes (50% My/My, 71% My/N, 55% N/N), but, only 4/10 My/My QH were competing. My/N horses achieved national or world championships or both. Conclusions: Approximately 20% of My/N QH develop rapid atrophy. Atrophy is more common (80%) in homozygous My/My QH and less likely to resolve. Inciting causes such as vaccination and infection are inapparent in over half of cases.
© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
Publication Date: 2022-04-14 PubMed ID: 35426178PubMed Central: PMC9151494DOI: 10.1111/jvim.16417Google Scholar: Lookup
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- Journal Article
Summary
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This research examines the prevalence of clinical signs and contributing factors to muscle atrophy and break down, linked to a mutation (MYH1) in Quarter Horses and related breeds, and what might trigger such reactions in these horses.
Methodology
- The horse breeds studied were those homozygous reference (N/N), heterozygous (My/N), and homozygous (My/My) for the MYH1 mutation. The sample size included 275 N/N, 100 My/N, and 10 My/My Quarter Horses.
- A retrospective case-control study was undertaken using a questionnaire filled out by clients of the Veterinary Genetics Laboratory at the University of California, Davis. This study analysed the history of clinical signs, disease, vaccination, and performance based on genotype.
Results
- Atrophy was found to occur more in horses with the MYH1 mutation than those without it. This condition was found more frequently in My/My horses than My/N ones.
- The study observed that My/My horses exhibited rapid muscle atrophy, with a recurrence rate of 50%. These horses also showed a lesser recovery rate compared to My/N horses.
- Stiffness was found to be a common condition across the genotypes studied.
- A notable observation was that 47% of MYH1 horses were vaccinated or had respiratory or gastrointestinal disease, three months before the atrophy and stiffness was observed.
- The achievement of 100% expected performance did not differ significantly across genotypes, even thoughonly four out of ten My/My Quarter Horses were competing. Meanwhile, My/N horses were found to achieve national or world championships.
Conclusions
- Roughly 20% of My/N Quarter Horses develop rapid atrophy, whereas the likelihood of this condition is higher (80%) in homozygous My/My Quarter Horses and its resolution probability is lower.
- The triggering factors such as vaccination and infection were found to be unapparent in more than half of the cases studied.
Cite This Article
APA
Valberg SJ, Schultz AE, Finno CJ, Bellone RR, Hughes SS.
(2022).
Prevalence of clinical signs and factors impacting expression of myosin heavy chain myopathy in Quarter Horse-related breeds with the MYH1E321G mutation.
J Vet Intern Med, 36(3), 1152-1159.
https://doi.org/10.1111/jvim.16417 Publication
Researcher Affiliations
- Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
- Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA.
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- Department of Population Health and Reproduction, Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California Davis, Davis, California, USA.
- University of California Davis, Davis, California, USA.
MeSH Terms
- Animals
- Case-Control Studies
- Horse Diseases / epidemiology
- Horse Diseases / genetics
- Horse Diseases / metabolism
- Horses
- Humans
- Muscular Atrophy / veterinary
- Muscular Diseases / veterinary
- Mutation
- Myosin Heavy Chains / genetics
- Prevalence
- Retrospective Studies
Grant Funding
- American Quarter Horse Foundation
- Mary Anne McPhail endowment at Michigan State University
- NCATS L40 TR001136 (CJF)
- University of California Davis Veterinary Genetics Laboratory
Conflict of Interest Statement
The authors declare no conflict of interest.
References
This article includes 13 references
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Citations
This article has been cited 1 times.- Durward-Akhurst SA, Valberg SJ. Myosin Heavy Chain Myopathy and Immune-Mediated Muscle Disorders. Vet Clin North Am Equine Pract 2025 Apr;41(1):61-75.
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