Emergence of Infectious Bronchitis Virus genotype GI-24 and GI-16 along with predominant circulation of genotype GI-1 in commercial poultry in Bangladesh

Figures

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  Fig. 1. Regional occurrence of IBV across different regions of Bangladesh. The map shows the number of positive IBV samples across different administrative divisions. The figure was created by using the website https://www.datawrapper.de.

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  Fig. 2. The heat map illustrates the correlation between viral load and clinical severity. Darker color intensities represent higher viral loads, which correspond to elevated clinical scores. In contrast, progressive lighter shades indicate lower viral loads associated with mild or minimal clinical manifestations. The figure was created using the GraphPad Prism 10.4.2.

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  Fig. 3. Embryonic changes are associated with infectious bronchitis virus infection. (A) Uninfected control embryo showing normal development. (B, C) IBV-infected embryos exhibit stunting, curling, dwarfism, and subcutaneous hemorrhage.

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  Fig. 4. Agarose gel electrophoresis showing amplification of the S1 gene of infectious bronchitis virus (IBV). A specific amplicon of approximately 1,000 bp is observed in positive samples when compared with the molecular weight ladder.

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  Fig. 5. Phylogenetic tree based on partial S1 gene sequences of 16 Bangladeshi infectious bronchitis virus (IBV) isolates together with 91 reference sequences retrieved from GenBank. The tree was constructed using MAFFT version 7 online tool (Katoh et al., 2019). The phylogenetic tree was constructed using the maximum likelihood method employing the GTR +G + I + F model and SH-like aLRT method for branch support via the NGPhylogeny online tool (Lemoine et al., 2019). The tree was annotated using iTOL. Bootstrap values are shown at the corresponding nodes, and GenBank accession numbers are indicated alongside strain names. Colors represent the three different genotypes as mentioned in the color range box. Star mark denotes Bangladeshi strains sequenced in this study.

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  Fig. 6. Estimates of evolutionary divergence among infectious bronchitis virus (IBV) sequences based on the number of base substitutions per site between sequence pairs. Analyses were performed using the Maximum Composite Likelihood model (Tamura et al., 2004) with the pairwise deletion option applied to ambiguous positions, resulting in a final dataset of 3,507 nucleotide positions. Evolutionary analyses were conducted in MEGA 12 (Kumar et al., 2024). Yellow shading indicates measurable genetic divergence between the newly introduced GI-24 genotype with reference vaccine strains, pink denotes genetic divergence between GI-16 genotype with reference vaccine strains, whereas green denotes negligible genetic variation among strains of GI-1field and vaccine strains.