Abstract
Aim:This study aimed to isolate some of the currently circulating infectious bronchitis virus (IBV) strains from some broiler chicken farms in Al-Hasa and to do some molecular characteristics of these strains.Materials and Methods:We collected 300 tissue specimens, including the trachea, bronchi, lungs, and kidneys from some four commercial chicken farms showing respiratory manifestations. We tested these tissue specimens by the real-time polymerase chain reaction (RT-PCR) and gel-based PCR. We selected some PCR positive samples for isolation in the embryonated chicken eggs (ECE). We sequenced some PCR-positive samples and conducted phylogenetic analysis based on the obtained sequences.Results:Our molecular surveillance revealed that 31.6% of the tested specimens were IBV positive by PCR. We selected some positive specimens showing low Ct values by the qRT-PCR for virus isolation by the ECE. The infected eggs showed hemorrhage, dwarfing, and death in some cases after three passages in the ECE. We sequenced some of the positive PCR specimens and used the obtained sequences to draw the phylogenetic tree based on the partial IBV-ORF-1a, N, and S1 gene sequences. The phylogenetic trees based on the IBV-N and S1 gene sequences showed that the circulating IBV strains in Al-Hasa during 2016 was showing a high degree of identity to some strains from Taiwan and Italy. Meanwhile, the grouping of these strains based on the IBV-S1 sequences revealed that the currently circulating IBV strains in Al-Hasa belonged to Gr.I.7 along with strains from Taiwan.Conclusion:Our results confirmed the continuous circulation of the IBV among the chicken population in Al-Hasa despite the intensive application of vaccines against this virus.
Highlights
Infectious bronchitis virus (IBV) is a highly contagious respiratory viral disease of chickens of all ages
We sequenced some of the positive PCR specimens and used the obtained sequences to draw the phylogenetic tree based on the partial infectious bronchitis virus (IBV)-ORF-1a, N, and S1 gene sequences
The phylogenetic trees based on the IBV-N and S1 gene sequences showed that the circulating IBV strains in Al-Hasa during 2016 was showing a high degree of identity to some strains from Taiwan and Italy
Summary
Infectious bronchitis virus (IBV) is a highly contagious respiratory viral disease of chickens of all ages. The IBV belongs to the order Nidovirales, family Coronaviridae, and genus Gammacoronavirus [1,2]. The IBV genome is a positive sense RNA molecule with a high tendency to frequent changes and recombination. There is a high degree of genetic diversity among IBV strains. There was no available system for the definite grouping and identification of various IBV genotypes. One recent study used the combination between the phylogenetic analysis and the pairwise similarities on both the nucleotides and the amino acid levels to do fine mapping of the IBV genotypes [3]. This study used the full-length S1 gene sequences to develop a novel classification
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