Beef cattle

Genetic Insights into Bovine Eosinophilic Myositis: From Field Data to Genomic Selection Strategies

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Abstract

Bovine Eosinophilic Myositis (BEM) is a muscle disease characterized by eosinophilic inflammation and myofiber degeneration. It is usually only detected at slaughter due to the absence of clear clinical symptoms. BEM manifests as gray-to-green discoloration of the most active muscles, resulting in carcass condemnation and significant economic losses estimated at €4-5 million per year for the French beef industry. The etiology of BEM remains unclear. Sarcocystis, an intracellular protozoan parasite found in lesions and capable of triggering an eosinophilic immune response, is suspected to be involved. However, Sarcocystis infection is highly prevalent in cattle worldwide whereas BEM cases are rare, suggesting that other factors influence disease onset. The GMyosEo2 project, funded by Apis-Gene, aimed to better understand disease prevalence, uncover the genetic background of BEM, and assess the potential of genetic selection as a management tool.Data from affected carcasses collected at slaughterhouses in five French regions over the past 10 years were analyzed and compared with healthy animals (more than 11 million females aged between 2 and 10 years). To further investigate the Blonde d'Aquitaine breed, a network of herds with a high prevalence of the disease and nearby herds without cases was established. Extensive environmental surveys were conducted and revealed only minor differences in herd management. Blood samples were collected from 150 slaughtered animals to investigate biomarkers as potential BEM indicators. A total of 2,400 females from the Blonde d'Aquitaine breed were sampled for cartilage before slaughter and for muscle tissue in cases of carcass condemnation. In the Blonde d'Aquitaine breed, a reference population was built by genotyping 269 condemned females and 1,300 related animals to perform a single-step genomic evaluation. Family trios (36 animals) were sequenced to identify genetic markers associated with susceptibility or resistance. A whole-genome sequencing-based GWAS was additionally performed in the Normande and Blonde d'Aquitaine breeds.Breed-specific prevalences were observed, with Blonde d'Aquitaine, Parthenaise, and Normande being the most affected breeds, showing condemnation rates ranging from 1 to 6‰ in females aged 2 to 10 years. Analyses of blood biomarkers revealed no reliable predictors of BEM in vivo, suggesting the need to investigate additional biomarkers. Heritability estimates for BEM resistance were 2.3% and 4.4% for Normande and Blonde d'Aquitaine breeds, respectively, supporting the feasibility of genetic selection. The GWAS highlighted several highly significant candidate regions on BTA5, BTA11, BTA16, BTA20, BTA23, and BTA25.Early detection of the disease is not yet possible; however, the genetic approach shows promise. Future steps include expanding condemnation data coverage nationwide, integrating identified SNPs into future EuroGMD bead chips, and deploying genomic management strategies in collaboration with breeding partners to minimize the risk of BEM-sensitive mating pairs.

Keywords: 2026

How to Cite:

Leclerc, H., Grohs, C., Arrieudarre, S., Drouet, M., Oudot, N., Baur, A., Escouflaire, C., Boussaha, M., Salesses, R., Plasse, P., Martin, P. & Fritz, S., (2026) “Genetic Insights into Bovine Eosinophilic Myositis: From Field Data to Genomic Selection Strategies”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286446. doi: https://doi.org/10.31274/wcgalp.24009

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