Unveiling the Molecular Crosstalk between Heat Stress, Vaccination, and E. coli Infection in Broilers

Escherichia coli infections pose a major threat to poultry health, with biofilm formation significantly contributing to disease. This study uniquely investigated the complex interactions between vaccination, an E. coli challenge, and heat stress on broilers, addressing a research gap that typically examines these factors in isolation. Vaccination proved highly effective, substantially reducing mortality and clinical signs while significantly lowering cecal E. coli load in challenged birds. At a molecular level, vaccination downregulated all four key biofilm genes and enhanced antioxidant enzyme expression. Our most notable finding was a statistically significant, synergistic inflammatory response in the triple-stressed group (vaccinated, infected, and heat-stressed), which exhibited the highest pro-inflammatory cytokine expression. These results underscore the importance of considering multiple stressors in poultry health. The findings directly inform poultry management by supporting vaccination as a comprehensive strategy to boost broiler resilience, particularly in regions prone to heat stress. Furthermore, this study provides a molecular roadmap for developing next-generation vaccines that not only elicit an immune response but also prime a bird's physiological systems to better cope with combined environmental and pathogenic challenges.