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Isolation and genetic analysis revealed no predominant new strains of avian infectious bronchitis virus circulating in South China during 2004-2008.

ABSTRACT: Twenty-seven strains of avian infectious bronchitis virus (IBV) were isolated from dead or diseased chickens at different chicken farms in South China during 2004-2008, of which the S1 gene was sequenced. Phylogenetic analysis of the S1 gene sequences of the isolated 27 strains together with 29 strains published in Genbank revealed that all IBV strains except for one isolated and one published were clustered into six distinct genotypes I-VI. 26 isolated strains belong to genotypes I, II, and III, forming a big phylogenetic branch without new predominant strains, whereas all five vaccine strains belong to genotype V that is evolutionarily distant from genotypes I, II, and III. The study of the protease cleavage motif within the S1 protein found 12 different cleavage motifs, of which 3 motifs are shared by both isolated and published strains, 2 motifs unique to isolated strains, and 7 motifs unique to published strains, further bolstering the notion of no new predominant strains. Alignment analysis of the S1 amino acid sequences indicated that the amino acid substitutions, insertions, and deletions are polymorphic and diverse, showing no sign of predominant genetic changes among the isolated strains. Taken together, there was no predominant new strain circulating in South China during 2004-2008. Nonetheless, circulating IBV strains have been continuously evolving with genetic compositions distant from vaccine strains; this explains why there have been constant but infrequent outbreaks in commercial flocks in South China during 2004-2008. Furthermore, in order to safe guard against the sudden emergence of new predominant strains, continuing surveillance of IBV strains circulating in the field is of extreme importance.

SUBMITTER: Li L

PROVIDER: S-EPMC7117290 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Isolation and genetic analysis revealed no predominant new strains of avian infectious bronchitis virus circulating in South China during 2004-2008.

Li Linlin L Xue Chunyi C Chen Feng F Qin Jianping J Xie Qingmei Q Bi Yingzuo Y Cao Yongchang Y

Veterinary microbiology 20091124 2-4

Twenty-seven strains of avian infectious bronchitis virus (IBV) were isolated from dead or diseased chickens at different chicken farms in South China during 2004-2008, of which the S1 gene was sequenced. Phylogenetic analysis of the S1 gene sequences of the isolated 27 strains together with 29 strains published in Genbank revealed that all IBV strains except for one isolated and one published were clustered into six distinct genotypes I-VI. 26 isolated strains belong to genotypes I, II, and III ...[more]

PMID: 20022714

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Project description:AimTo characterize the circulating infectious bronchitis virus (IBV) strains in Egypt depending on the sequence of the spike-1 (S1) gene [hypervariable region-3 (HVR-3)] and to study the pathotypic features of these strains.MethodsIn this work, twenty flocks were sampled for IBV detection using RRT-PCR and isolation of IBV in specific pathogen free (SPF) chicks during the period from 2010 to 2015. Partial sequencing and phylogenetic analysis of 400 bp representing the HVR-3 of the S1 gene was conducted. Pathotypic characterization of one selected virus from each group (Egy/Var-I, Egy/Var-II and classic) was evaluated in one day old SPF chicks. The chicks were divided into 4 groups 10 birds each including the negative control group. Birds were inoculated at one day by intranasal instillation of 10(5)EID50/100 μL of IBV viruses [IBV-EG/1212B-2012 (Egy/Var-II), IBV/EG/IBV1-2011 (Egy/Var-I) and IBV-EG/11539F-2011 (classic)], while the remaining negative control group was kept uninfected. The birds were observed for clinical signs, gross lesions and virus pathogenicity. The real-time rRT-PCR test was performed for virus detection in the tissues. Histopathological examinations were evaluated in both trachea and kidneys.ResultsThe results revealed that these viruses were separated into two distinct groups; variant (GI-23) and classic (GI-1), where 16 viruses belonged to a variant group, including 2 subdivisions [Egy/Var-I (6 isolates) and Egy/Var-II (10 isolates)] and 4 viruses clustered to the classic group (Mass-like). IBV isolates in the variant group were grouped with other IBV strains from the Middle East. The variant subgroup (Egy/Var-I) was likely resembling the original Egyptian variant strain (Egypt/Beni-Suif/01) and the Israeli strain (IS/1494/2006). The second subgroup (Egy/Var-II) included the viruses circulating in the Middle East (Ck/EG/BSU-2 and Ck/EG/BSU-3/2011) and the Israeli strain (IS/885/00). The two variant subgroups (Egy/Var-I and Egy/Var-II) found to be highly pathogenic to SPF chicks with mortalities up to 50% than those of the classic group which was of low virulence (10% mortality). Pathogenicity indices were 25 (Egy/Var-II), 24 (Egy/Var-I) and 8 (classic); with clinical scores 3, 2 and 1 respectively.ConclusionThese findings indicated that the recent circulating Egyptian IBVs have multiple heterogeneous origins in marked diversifying nature of their spread, with high pathotype in specific pathogen free chicks.

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Isolation and genetic analysis revealed no predominant new strains of avian infectious bronchitis virus circulating in South China during 2004-2008.

Publications

Isolation and genetic analysis revealed no predominant new strains of avian infectious bronchitis virus circulating in South China during 2004-2008.

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