Molecular Monitoring of D1466 Genotype of Avian Infectious Bronchitis Virus in Iran: A Retrospective Study in 2013-2017.

Infectious bronchitis is one of the most common diseases in the poultry industry in many countries, especially in the regions with a dense poultry farming industry. Gammacoronavirus is the etiologic agent of this disease, with the chickens and poultries as the natural reservoirs of the virus. Various strains of infectious bronchitis virus have been reported in poultry around the world. In terms of pathogenicity, this virus can induce a spectrum of diseases ranging from the moderate respiratory tract to kidney and reproductive diseases. The serotypes of this virus do not cause cross-immunity against each other. This issue makes it difficult to control the disease. Based on the analysis of the highly variable region of the glycoprotein S1 gene, the isolated strains in Iran were classified into seven different phylogenetic groups, including Massachusetts, QX, IS-720, IS-1494, 793/B, IR-1, and IR-2. The D1466 genotype has not been reported in the country; however, the killed vaccine is used in broiler breeder farms. In this study, tissue specimens were collected from 700 farms (i.e., broiler, egg-laying, and broiler breeder farms) suspected of infectious bronchitis within 2013-2017. The samples were examined using real-time reverse transcription-polymerase chain reaction. The D1466 genotype was not detected in any of the studied specimens. Due to the lack of immunity of the D1466 serotype against the dominant types in the country, one has to be careful in choosing the right vaccine. It is necessary to perform continuous monitoring of the circulation status of the various serotypes of viruses in the country to identify the dominant and possible new serotypes for the utilization of the appropriate vaccine.