1Animal Biotechnology Centre, Nanaji Deshmukh Veterinary Science University, Jabalpur, M.P., 482004, India
2Aquatic Animal Health, Central Institute of Fisheries Education, Mumbai, 400061, India
*Corresponding author: drhemlatajain@gmail.com
Online published on 4 November, 2016.
In India the most common vaccine strain against infectious bronchitis (IB) virus (IBV) is Mass strain (M41). Most of the organized and unorganized poultry farms use Mass strain for vaccination of parent stock. But even after taking all precautions the incidences of IB outbreak are common in poultry population. IBV, a major pathogen of poultry flocks, circulates in the form of several genotypes and serotypes. Only a few amino acid changes in the S1 subunit of wild type proteins may results in mutants unaffected by current vaccine. In the year 2008 one strains of IBV was isolated from vaccinated chicken flocks. The results from sequencing of S1 gene showed that this strain was distinct from classic IBV strains of H120, M41 etc. Compared to H120 and M41 vaccine strain, point mutation occurred at many positions in the S1 protein of this field strain. The homology of the nucleotide and amino acid sequences of the S1 gene of this isolate was 79.0%-99.6% and 74.5%-98.8%, respectively with relation to major vaccine strains used worldwide. The results from this study indicate that different IBV strains cocirculate in the chicken population in India.
Sequencing of S1 gene of Indian field isolate represents a unique sub-genotype.
These findings indicated that several other unknown genotypes may be circulated in field condition.
Results validate the need of permanent monitoring of circulating strains to make effective vaccination strategies.
Infectious bronchitis, IBV, spike protein, S1 gene, phylogenetic analysis
