Investigating the pathogenicity of novel non-pathogenic Avibacterium paragallinarum isolates and their protective potential against infectious coryza

< 0.05). Four weeks later (Phase II), G1-G7, as well as the original positive control group, were re-challenged with the same C1 isolate to assess protection. G1-G7 developed clinical signs, infraorbital sinus gross and histopathological lesions comparable to the new positive control. In conclusion, the study results match field observations and confirm the novel npAP isolates are non-pathogenic to chickens. Additionally, npAP isolates do not confer protection against circulating Midwestern pAP serovar C1. Given their prevalence in NHL flocks in the US, npAP should be ruled out before confirming IC diagnosis in flocks without clinical signs.