Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Virol. Aug 12, 2016; 5(3): 125-134
Published online Aug 12, 2016. doi: 10.5501/wjv.v5.i3.125
Genotyping and pathotyping of diversified strains of infectious bronchitis viruses circulating in Egypt
Ali Zanaty, Abdel-Satar Arafa, Naglaa Hagag, Magdy El-Kady
Ali Zanaty, Abdel-Satar Arafa, Naglaa Hagag, Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Giza 12618, Egypt
Magdy El-Kady, Department of Poultry Diseases, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef 62511, Egypt
Author contributions: The study was designed by Arafa AS and El-Kady M; data were collected and analyzed by Zanaty A; Arafa AS and Hagag N; data interpretation and manuscript preparation were undertaken by Zanaty A and Arafa AS.
Institutional review board statement: The study was reviewed and approved by Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute.
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Institutional Animal Care and Use Committee of the Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute.
Conflict-of-interest statement: All authors declared that there is no potential conflict of interests regarding this article.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Abdel-Satar Arafa, PhD, Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, P.O. Box 264-Dokki, Giza 12618, Egypt.
Telephone: +20-3-3380121 Fax: +20-3-3370957
Received: March 15, 2016
Peer-review started: March 17, 2016
First decision: April 18, 2016
Revised: May 26, 2016
Accepted: July 11, 2016
Article in press: July 13, 2016
Published online: August 12, 2016

AIM: To 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.

METHODS: In 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 105EID50/100 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.

RESULTS: The 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.

CONCLUSION: These 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.

Keywords: Infectious bronchitis virus, Phylogenetic analysis, Variant infectious bronchitis virus, S1 gene, HVR-3 Sequencing, Egypt

Core tip: Infectious bronchitis became enzootic in Egypt with frequent outbreaks of different variant in broiler chickens in spite of intensive vaccination programs used causing severe infections. These manuscripts discuss the prevalence of these different variants with pathotyping of these variants in specific pathogen free chicks.