Document Type: Full paper (Original article)
Centralized Research Laboratory, Department of Veterinary Microbiology, Veterinary College and Research Institute, Tamil Nadu Veterinary and Animal Sciences University, Namakkal, TN, India
Background: Infectious bronchitis virus (IBV), the etiological agent of an acute and highly contagious disease, infectious bronchitis (IB) that affects chicken of all ages and poses major economic loses to the poultry industry worldwide. Continuous evolution of the spike protein (S1) of IBV is responsible for the prevalence of many serotypes/genotypes around the world. Multiple lineages of IBV strains could be detected in India since 2003 from chicken flocks. Aim: Detection of IBV genotypes prevalent in India. Methods: Organ samples from 20 IBV-positive flocks with variable clinical signs were used for the amplification of the S1 gene of IBV by RT-PCR. Results: Positive PCR amplicons were sequenced. Sequence analysis showed that fourteen field isolates belonged to the GI-1 genetic lineage (Mass 41 serotype) while two field isolates belonged to GI-13 (4/91 strain), one of the field isolates grouped with GIII, GV and GVI genetic lineage and three belonged to a variant genotype unique to India (GI-24). Phylogenetic analysis also showed a similar type of grouping within the field isolates. Among the fourteen GI-1 (Mass 41 serotype) isolates, twelve were isolated between 2003 and 2006 and two only were isolated between 2009 and 2011. Two field isolates belonged to GI-13 were isolated in 2007, one belonged to GIII, GV and GVI was isolated in 2010 and three field isolates were not close to any reference IBV sequences which were isolated in 2006 (IND-TN-168-06), 2010 (IND-TN-280-10) and 2011(IND-TN-290-11). Conclusion: There is an emergence of a unique variant IBV in India (GI-24). Our findings will have important implications in future vaccine intervention.