Abstract

The infectious bronchitis virus (IBV) is one of the most important Coronaviridae viruses, infecting the upper respiratory tract of chickens and leading to considerable losses in the poultry industry across the globe. Many outbreaks have recently occurred among IBV-vaccinated chicken farms in the Diyala Governorate of Iraq resulting in significant economic losses. As a result, the purpose of the present study was to investigate whether IBV can be a source of infection spread in IBV-vaccinated commercial broiler flock farms in Diyala Governorate. In this regard, ELISA was used as a serological test and RT-PCR as a molecular detection technique. Serum samples were collected from chickens suspected of IBV at 16 and 23 days of age. The results showed a significant increase of IgG antibodies in such serum samples at days 16 and 23 of age indicating the infections of the broilers with IBV. However, at the age of 2-3 weeks, the samples of kidney, liver, trachea, and lungs were collected from clinically and sub-clinically infected flocks, and also postmortem samples were sampled from all farms. Two sets of previously reported primers were created for this purpose in the S1-protein gene region. According to the findings of the present investigation, IBV was found in 83 of samples. Finally, despite immunization with IB4/91, IBV was prevalent in broiler chicken farms in the study area confirmed by serology and molecular biology tests. This finding indicates the possibility of genetic difference between the locally discovered IBV and the administered IBV vaccine. A study on the production of local vaccines can be useful in controlling IBV infections. © 2022