Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria
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RESEARCH ARTICLE
Open Access
Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria Tamara Al-Jallad1,2, Morshed Kassouha3*, Mohamad Salhab1, Anouar Alomar4, Mouhamad AL-Masalma5 and Fahim Abdelaziz6
Abstract Background: Avian Infectious Bronchitis Virus (IBV) is a highly contagious disease that imposes a huge economic burden on the global poultry industry. IBV contains numerous serotypes and variants with incomplete tenuous cross immunological protection. The failure of currently used vaccines to protect against diverse, circulating IBV strains that are specific to a given region poses a major problem for the poultry industry. Thus, there is an urgent need to conduct studies aimed at genotyping field IB viruses. In this study, we have determined the molecular characteristics of circulating IBV by sequencing the S1 gene of viral isolates from affected previously vaccinated broiler flocks suffering from the disease. Results: Ten isolates propagated in embryonated eggs showed an ability to induce typical IBV lesions after three successive viral passages. We performed a nested RT–PCR assay that targeted the hypervariable region 3 (HVR-3) of the S1 gene, and identified the isolates as IBV through sequence analysis. The IBV isolates showed sequence similarity between the Syrian isolates that vary from 96.20 to 100%, and those being closer to the Variant-2 strain IS/ 1494/06 (EU780077.2) with 97.5 to 99.4% similarities. However, less nucleotide identity was found with sequences belonging to the used vaccine strains such as H120, Mass5, and 4/91. Conclusions: This study showed the presence of the Variant-2 strain circulating in Syrian broiler flocks showing signs of IBV disease. Currently, there is no commercial effective vaccine which protects birds against the Variant-2 strain. Continuous monitoring procedures should be taken to control and limit the spread of the IBV Variant-2 strain. This research emphasizes both the importance of epidemiological monitoring in intensive poultry farming for novel pathogens and the use of local isolates as future vaccine targets. Keywords: Infectious bronchitis virus, Molecular characterization, Broiler, Syria
* Correspondence: [email protected]; [email protected] 3 Department of Microbiology, Faculty of Veterinary Medicine, Hama University, Hama, Syria Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article
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