Delmarva (DMV1639) infectious bronchitis virus infection alters the microbiome of gastrointestinal and respiratory tracts of broiler chickens.

Infectious bronchitis virus (IBV) is known to cause significant alterations in tracheal microbial flora in broiler chickens 5 days post-infection (dpi) and our focus is to understand the changes in both respiratory and gastrointestinal microbiome in broilers over a period of time following IBV infection. A study was conducted to characterize the tracheal and cecal microbiome in IBV infected and control broiler chickens at 6, 9 and 15 dpi. IBV genome in trachea, lung and cecal tonsils could be observed in the infected group at all the time points. Immune response parameters and histopathological lesion scores were significantly higher in IBV infected trachea and cecal tonsils at 6, 9 and 15 dpi compared to the controls. We observed that cecal microbial diversity (alpha diversity) was increased in the IBV infected group at 6 and 15 dpi. On the other hand, diversity (alpha diversity) of tracheal microbiome was elevated only at 9 dpi in the IBV infected group. Moreover, significant shift of microbial communities (beta diversity), in both cecum and trachea was observed following IBV infection. Enzyme and metabolic pathway analyses of cecum indicated an upregulation of DNA replication and cell wall synthesis pathways and a downregulation of pathways related to short chain fatty acid (SCFA) production in the IBV infected group compared to the controls. Analysis of tracheal metabolic pathways suggested initial adaptation to the infection stress and gradually shifting to enhanced microbial growth and stability. The study outcome adds to the understanding of microbiome changes secondary to histological changes and immune response following IBV infection in broiler chickens.