Riemerella anatipestifer (R. anatipestifer) infection is a significant cause of duck serositis, characterized by high mortality and resulting in substantial economic losses globally. Waterfowl, turkeys and wild birds have traditionally been recognized as reservoirs for R. anatipestifer. However, recent reports indicate an increasing incidence of infections in chickens. This study presents the whole-genome analysis of the RA-C01 strain isolated from broiler chickens in China. Phylogenetic analysis revealed that this strain clusters within a small branch alongside the HXb2 strain of duck origin and within a larger branch with the 20190604J2-1 strain of chicken origin. The results of the antibiotic susceptibility test (K-B method) showed that the RA-C01 strain was susceptible to Ceftiofur sodium, Florfenicol and Levofloxacin. Animal infection experiments demonstrated that the RA-C01 strain induces lethargy and lameness in SPF chickens without causing mortality, while pathological examination revealed pericarditis, perihepatitis, air sacculitis, peritonitis, purulent exudation in joint and keel bone. The pathogenicity of the RA-C01 strain in ducks was found to be mild. SPF chickens immunized with an inactivated vaccine derived from the RA-C01 strain were challenged 14 days post-immunization. Results indicated that the immunized group exhibited no clinical or pathological symptoms upon challenge. This study establishes a stable R. anatipestifer infection model in chickens and demonstrates its immunogenic potential for the first time, providing valuable insights for future vaccine development.

To Cite This Article: Huang D, Wang R, Liu S, Shao Y, Zhang Z, Yu C, Bao S and Cong Y 2025. Genomic analysis and evaluation of pathogenicity and immunogenicity of Riemerella anatipestifer isolates from chickens in China. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.221