Coinfection with infectious bronchitis virus exacerbates the pathogenicity of Riemerella anatipestifer in chickens

Introduction Since its initial isolation from chickens, Riemerella anatipestifer has emerged as an increasingly prevalent pathogen in major poultry-producing regions, causing substantial economic losses, particularly through reduced egg production. Methods In the present study, an epidemiological investigation was conducted to detect coinfected pathogens in R. anatipestifer -positive clinical samples. Based on the epidemiological findings, the impact of coinfection with infectious bronchitis virus (IBV) on the pathogenicity of R. anatipestifer was evaluated in specific-pathogen-free (SPF) chickens. Results Epidemiological analysis revealed that IBV was the most frequently detected coinfecting pathogen (11.43%) in R. anatipestifer -positive samples. Animal challenge experiments demonstrated that bacterial loads in the liver, spleen, and brain were significantly higher in coinfected chickens than in those infected with R. anatipestifer alone. Notably, the incidence of oviduct obstruction was markedly elevated in the coinfected group (100%) compared to the group infected solely with R. anatipestifer (40%). Discussion These results suggested that IBV coinfection exacerbated the pathogenicity of R. anatipestifer in chickens. These findings highlight the critical role of polymicrobial interactions in modulating bacterial virulence and provide a foundation for developing integrated control strategies against R. anatipestifer .