Scuticociliatosis, a devastating parasitic disease caused by Miamiensis avidus, poses significant challenges in olive flounder (Paralichthys olivaceus) aquaculture due to high morbidity and mortality rates. While vaccination offers a promising disease management approach, it does not ensure complete efficacy across all fish, likely due to genetic variation in immune responses. Genomic selection and prediction are essential for identifying individuals with strong immune responses, enabling breeders to select disease-resistant candidates more effectively than the traditional pedigree-based methods. This study investigated the genetic basis of resistance to scuticociliatosis after vaccination, aiming to support selective breeding for disease-resistant olive flounder.
A cohort of 474 fish from 141 full-sib families received a formalin-killed vaccine followed by a challenge test with M. avidus. A custom high-density 70K SNP genotyping array was used to estimate genetic parameters, perform a Genome-wide Association (GWAS), predict genomic breeding values, and estimate its accuracy for host resistance to scuticociliatosis.
The results revealed significant genetic variation in post-vaccination resistance, with heritability estimated at 0.10. We identified 16 significant SNPs across several chromosomes using GWAS, with candidate genes linked to immune response pathways. Various prediction models were constructed to estimate host resistance traits, with Bayesian Lasso (BL), Bayesian B (BB), and Bayesian C (BC) achieving the highest accuracy. Prediction ability increased with the number of SNP markers and population size. Furthermore, by selecting significant SNPs based on GWAS to build a prediction model, the prediction ability increased significantly to 0.545, compared to 0.091 with randomly selected markers.
These findings offer valuable insights into host resistance to scuticociliatosis, facilitating improved selective breeding strategies in olive flounder aquaculture.