Molecular detection and epidemiological distribution of poultry respiratory viral pathogens in commercial chicken flocks in Bangladesh

Respiratory viral infections have a considerable detrimental impact on animal health as well as significant financial consequences in the poultry industry. The primary aim of this study is to investigate the major pathogens involved in respiratory diseases of poultry, the co-infection rate, and their epidemiological distribution in commercial chicken farms in Bangladesh. From June 2022 to December 2023, 300 pooled samples (swabs from live birds, and respiratory tissues from dead birds) were collected from the selected poultry farms where respiratory outbreaks were noticed. Samples were screened for five important respiratory pathogens circulating in Bangladesh including H9N2 low pathogenic avian influenza virus (LPAIV), H5N1 highly pathogenic avian influenza virus (HPAIV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and infectious laryngotracheitis virus (ILTV). One-step qPCR was performed using either TaqMan probe-based or SYBR Green chemistry. A total of 140 flocks (46.67 %) were found infected with these respiratory pathogens including 18.57 % H5N1(n = 26), 20 % H9N2 (n = 28), 50 % IBV (n = 70), 37.15 % NDV (n = 52), 0.71 % ILTV (n = 1) and 26.40 % (n = 37) mixed infections were present. The present study also revealed that co-infection of several respiratory pathogens (26.40 %) caused more serious synergistic pathogenic effects and complicating factors in poultry infections. In Bangladesh, for this study, the most common season for infections in layer, broiler, broiler breeder, and Sonali is spring where these infections exhibited a consistent pattern. Nevertheless, the investigation revealed the continuous co-circulations of various respiratory viruses, resulting in a complex environment in the poultry industry. This information also helps raise farmer-level disease awareness to prevent and control the spread of viruses.