Research progress on <i>Avibacterium paragallinarum</i> and related bacterial and viral diseases in poultry and their mixed infections.

Avibacterium paragallinarum (A. paragallinarum) is one of the primary pathogens causing respiratory diseases in poultry flocks, posing a serious threat to the health and production efficiency of the global poultry industry. With the expansion of modern farming scales and changes in environmental factors, mixed infections involving A. paragallinarum alongside other bacteria and viruses have become increasingly prevalent. This has led to more complex and diverse disease manifestations, significantly increasing the difficulty of prevsention and control. Current research on A. paragallinarum encompasses its antigenic structural characteristics, vaccine development and optimization, and therapeutic strategies. However, gaps remain in the profound understanding of mixed infection mechanisms and synergistic control approaches. This manuscript systematically summarizes recent advances in research concerning A. paragallinarum and its associated bacterial and viral co-infections. It focuses on analyzing the impact of antigenic variation on vaccine efficacy, the status of composite vaccine development, and the pathological mechanisms of multi-pathogen synergistic infection. The aim is to provide a theoretical foundation and practical reference for the comprehensive prevention and control of A. paragallinarum-related diseases, thereby promoting the healthy and sustainable development of the poultry farming industry.