Abstract
BackgroundInfectious bronchitis virus (IBV), a major pathogen of commercial poultry flocks, circulates in the form of several serotypes/genotypes. Only a few amino-acid changes in the S1 subunit of wild-type IBVS proteins may result in mutants unaffected by current vaccines.MethodsPartial S1 gene sequences of 3 IBV isolates of the Moroccan Italy 02 genotype from vaccinated and unvaccinated broiler chicken flocks, located in southern and central regions of Morocco, were amplified by RT-PCR, sequenced, and aligned for phylogenetic and amino-acid similarity analyses.ResultsThe three isolates were found genetically highly distant from known avian IBV based on partial sequences of their S1 genes: gammaCoV/chicken/Morocco/I01/2011(IBV/Morocco/01), gammaCoV/chicken/Morocco/I30/2010 (IBV/Morocco/30), and gammaCoV/chicken/Morocco/I38/2013 (IBV/Morocco/38), nucleotide sequence identities reached 89.5 % to 90.9 % among the three isolates. The deduced protein sequence identities ranged from 29.7 % (between IBV/Morocco/38 and Egypt SCU-14/2013-1) to 78.2 % (between IBV/Morocco/01 and Spain/05/866). Amino acid sequence comparison and phylogenetic analysis indicated the emergence of a new Moroccan genotype, clustering with regionally related isolates from Spain (Spain/05/866) and belonging to a new sub-genotype.ConclusionOur sequencing results demonstrate a co-circulation of wild-type infectious bronchitis viruses in broiler chickens. These results justify permanent monitoring of circulating strains in order to rationally modify vaccination strategies to make them appropriate to the evolving field situation.
Highlights
Infectious bronchitis (IB) is one of the most contagious diseases that affect poultry worldwide and is responsible for severe economic losses
Case history Infectious bronchitis was diagnosed between January 2010 and December 2013 in southern and central regions of Morocco
The present study suggests that a new genotype, represented by the three new Infectious bronchitis virus (IBV) isolates described here, has been circulating in Morocco since at least 2010 (IBV/Morocco/30, accession number: KJ701020)
Summary
Infectious bronchitis (IB) is one of the most contagious diseases that affect poultry worldwide and is responsible for severe economic losses. Infectious bronchitis virus (IBV) is a member of the species Avian coronavirus, genus Gammacoronavirus (Nidovirales: Coronaviridae: Coronavirinae) [4]. IBV particles consist of three major structural proteins: spike (S) glycoprotein, membrane (M) protein, and nucleocapsid (N) protein. The spike of IBV is formed by post-translational cleavage of S into two separate polypeptide components, S1 and S2 [5, 6]. Genotype evolution of IBV is associated primarily with changes in the S1amino-acidsequence [7, 8]. Infectious bronchitis virus (IBV), a major pathogen of commercial poultry flocks, circulates in the form of several serotypes/genotypes. A few amino-acid changes in the S1 subunit of wild-type IBVS proteins may result in mutants unaffected by current vaccines
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