Change of pathotype and phylogenetic analysis of infectious bronchitis virus detected in Kagoshima prefecture, Japan

Infectious bronchitis (IB) is a highly contagious disease in chickens, induced by IB virus (IBV) infection. The pathotype and S1 genotype of IBV field strain that was detected from 2008 to 2018 were investigated in Kagoshima prefecture, Japan. The frequency of cases that the renal lesion characteristic of IBV infection was histopathologically confirmed was significantly higher from 2014 to 2018 than from 2008 to 2009, suggesting the altered pathotype of IBV. Of 7 genotypes (JP-I, JP-II, JP-III, JP-IV, Mass, Gray, and 4/91) that have been detected in Japan, 6 genotypes except for JP-II were detected since 2008 and it appeared that the JP-III and JP-I have been predominant. The JP-IV with different antigenicity from other genotypes was detected since 2009.