Molecular serotyping and virulence assessment ofstrains circulating in Chinese poultry flocks.

Abstract

BACKGROUND: Infectious coryza, caused by(), is a highly contagious respiratory disease that poses a significant threat to poultry production in China. Updated information on the epidemiology, serotype distribution, and virulence of circulating strains is essential for formulating effective regional control and vaccination strategies. METHODS: A total of 200 clinical samples from nine provinces were analyzed to determine the prevalence, serotype distribution, and seasonal dynamics of. The bacterial isolation, characterization, species-specific PCR, and molecular serotyping based on thegene were performed. Phylogenetic relationships were inferred using the neighbor-joining method. The pathogenicity of representative isolates (serotype A and C) was assessed using SPF chickens. RESULTS: prevalence varied geographically, with the highest isolation rates in Anhui, Guangxi, and Guangdong provinces, and no detection in Sichuan or Hubei. A distinct seasonal pattern was observed, with peaks in late autumn and winter. 22 isolates were recovered and serotyped: serotype A predominated ( = 15), followed by serotype C ( = 5), and serotype B ( = 2). Phylogenetic analysis ofrevealed clear clustering congruent with serotype classification. Both serotypes induced typical infectious coryza, with directly inoculated birds exhibiting more severe clinical signs than contacts. CONCLUSION: This multi-provincial study provides contemporary insights into the epidemiology, serotype distribution, and virulence ofin China. These findings underscore the necessity for region-specific surveillance and support the development of targeted vaccines based on locally prevalent, virulent strains.