Concurrent infection of Infectious Bronchitis Virus and Mycoplasma gallisepticum in a backyard poultry

This study reports the co-existence of two S1 mutants of GI-13 (4/91-like) Infectious Bronchitis Virus (IBV) and Mycoplasma gallisepticum (MG) in a backyard poultry flock that had non-vaccinated 30 broiler chickens and four turkey pullets. Serum samples and tracheal swabs were taken from the chickens and turkey pullets showing respiratory signs. Serum antibody levels were measured using commercial ELISA kits against IBV, Avian Influenza Virus (AIV), Newcastle Disease Virus (NDV), Avian Metapneumovirus (AMPV), MG, Mycoplasma synoviae (MS), and Ornithobacterium rhinotracheale (ORT). Additionally, tracheal swabs were tested for AIV serotypes H5, H7, and H9, NDV, IBV, AMPV, MG, MS, Pasteurella multocida, , Avibacterium paragallinarum, , and Bordetella avium by circular amplification technology (CAT). Anti-MS,-IBV,-MG,-NDV,-AMPV, and-ORT IgG antibodies were detected in some chicken sera, while anti-NDV,-MG,-MS, and-ORT IgG antibodies were detected in turkey sera. All avian tracheal swabs were positive for MG. However, IBV was only detected in chicken tracheal samples tested by CAT. The IBV strains were genotyped by sequencing a part of the S1 glycoprotein gene. The alignment analyses of two isolates showed 99.35% and 98.69% nucleotide similarities and 99.02% amino acid similarities with the 4/91 IBV vaccine and field strains. Two mutants showed 99.35% nucleotide and 100% amino acid sequence identity to each other. The turkeys and chickens in the flock had MG and MG/IBV co-infections, respectively. Consequently, the presence of mutants of 4/91 (GI-13) IBV genotypes and MG found in backyard poultry could be a potential epidemiological source for commercial flocks in poultry integrations.