Molecular Identification of Wild Type Strains of Infectious Bronchitis Virus in Vaccinated Broiler flocks in Mazandaran Providence

Infectious bronchitis is one of the major problems in the poultry industry in the world. Molecular and epidemiological studies, as well as continuous identification of genetic variants among common viruses in farms, play an important role in controlling, preventing and designing effective vaccines against disease. In the current study, chicken flocks with suspected infections bronchitis virus (IBV) were examined in Mazandaran province. Tracheal swab specimens were collected from 28 broiler chickens with respiratory symptoms in northern Iran in autumn and winter of 1396. Mortality rates of 15 to 25 percent were reported in studied flocks. Polymerase Chain Reaction (PCR) was used to amplify the virus replicase gene using specific primers. The reference strain was the H120 bronchitis vaccine. Direct sequencing method was used to identify wild strains from vaccine strains. In the preliminary test, 82% (23/28) of the suspected farms has shown the presence of IBV. Using the sequencing analysis, 5 wild strains were detected in the infected flocks (19 farms), indicating a high diversity in the population under study. The results of this study showed that emerged of new strains of infectious bronchitis virus in broiler flocks in Mazandaran province could be related to breeding conditions such as high density and repeated vaccination and different type of vaccines.