Molecular characterization of isolated infectious bronchitis viruses from affected vaccinated broiler flocks in Syria

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.

Diagnosis of Infectious Bronchitis Infection in Broiler Chicken Farms in Salah Al-Din Governorate

“…The prototypical coronavirus known as the infectious bronchitis virus causes millions of dollars' worth of annual losses for the poultry industry globally [2,3]. Infectious bronchitis affects birds of various ages and results in respiratory problems such as breathing difficulty, tracheal rattling, panting, coughing, and sneezing with or without facial swelling, frothy discharge in the eyes, nasal mucous discharge, and general weakness, with the young chicks huddling under the heat sources [4,5]. Some IB variant strains affecting the urinary system, especially the kidneys [6,7].…”

The use of RT-PCR in the diagnosis and differentiation of vaccine strains of chicken infectious bronchitis and Newcastle disease

“…Several PCR options allow you to highly reliably determine the genotypic structure of the virus and attribute it to a specific strain. Most often, for the quantitative and qualitative determination of the incidence in birds caused by RNA-containing viruses, the real-time reverse transcription polymerase chain reaction (qRT-PCR or RT-PCR) method is used ( Shanmuganathan et al, 2017 ; Okino et al, 2018 ; Al-Jallad et al, 2020 ; Mo et al, 2020 ; Salem et al, 2020 ; Ongor et al, 2021 ; Worku et al, 2022 ) for the typing of the chicken IBV as well as for the isolation of the NDV. The difference between the methods of different researchers was using various primers and probes for typing viral strains.…”

Comparison of Field and Hatchery Practices in Spray Vaccination Against Infectious Bronchitis

“…Aşılamadan 3-5 gün sonra trakede bulunan aşı virüsü bağışıklığı indükleyen mekanizmaları harekete geçirerek hücresel bağışıklık oluşmasına katkı sağlamaktadır [31], [32]. Bu aralık günlerinde alınan örnekleme çalışmalarında optimum doğruluk ile virüs tespiti sağlanmaktadır [33], [34]. Çalışmalarda virüsün trakedeki replikasyonu sırasında trakeal sürüntü ile alınan örneklerde aşı virüsünün saptandığı rapor edilmiştir.…”