Infectious Bronchitis Virus Detection and Isolation from Broiler Chicken

Infectious bronchitis virus was detected in tissue samples of 16.39% (n=10) non-vaccinated commercial broiler flocks showing respiratory and or nephrotic lesions by real time RT-PCR and RT-PCR amplification of 5’-UTR and N gene. Tissue/swab suspensions from all 10 flocks were inoculated in 9–11 day old SPF embryonated chicken eggs by allantoic route. Nephropathogenic IBV was isolated from samples of 2 farms from Vijaywada region of Andhra Pradesh. Necropsy of birds from above two farms revealed lesions of swollen and mottled kidneys in many birds and visceral gout in few birds. Histopathological examination confirmed nephropathogenicity of the isolates. S1 gene amplification from two IBV isolates viz. BVC/2017/VSD/IBV/South/1 and BVC/2017/VSD/South/2 and subsequent sequencing revealed 92.7 to 96% amino acid sequence identity with the sequences of Indian nephropathogenic isolates published earlier. Amino acid sequences of two isolates shared 73.8%, 75.3% and 72.1% identity with M41, H120 and 4–91 type as respectively, which indicated substantial genotypic divergence from M41 and H120 (major respiratory and vaccine strain) and 4–91 strain. Of the samples from 8 flocks with respiratory lesions (positive for IBV by RT-PCR however, negative on isolation); 6 were found positive for Mycoplasma gallisepticum and or Avian influenza (H9) by PCR and RT-PCR test respectively.