Inter-breed comparison results indicate that JR ducks exhibited lower mortality and morbidity compared to WK ducks under RA infection; while susceptible individuals in both breeds showed severe weight loss, splenomegaly, and multiorgan histopathology, and resilience mechanisms diverged critically: resistant JR ducks maintained stable growth, normal spleen indices, minimal lesions, physiological iron homeostasis, and mounted an IL-17A-elevated response with stable IgA/Th1/Th2 cytokines. This evidence concerns the gene IL17A and Splenomegaly.