Molecular Genotyping and Pathogenicity Study for Avian Infectious Bronchitis Virus Currently Epidemic in Chicken Flocks in Egypt during 2021

Amer, Sameh Abdel-Moez; Magdy Ahmed, Hagar; Mahmoud Maatouq, Asmaa

doi:10.21608/ejvs.2023.232254.1578

Molecular Genotyping and Pathogenicity Study for Avian Infectious Bronchitis Virus Currently Epidemic in Chicken Flocks in Egypt during 2021

Document Type : Original Article

Authors

¹ Department of Poultry Diseases, Veterinary Research Division, National Research Centre, P.O. Code 12622, Dokki, Cairo, Egypt

² Department of Poultry Diseases, Veterinary Research Institute, National Research Centre, P.O. Code 12622, Dokki, Cairo, Egypt

10.21608/ejvs.2023.232254.1578

Abstract

Infectious bronchitis virus (IBV) became endemic in Egypt with multiple outbreaks in both broiler and layer chickens despite the heavy vaccination regimens. The aim of the current study is to determine the genotypic and pathotypic characteristics of the currently circulated IBVs in different Egyptian governorates. Thirty chicken flocks with a vaccination history against IB were screened using egg propagation and reverse transcriptase-PCR assay targeting the spike protein gene (S) and further full-length S1 gene sequence analysis was also carried out. As well as, the pathotypic features of the obtained IBV isolates was assessed by challenge trail in 25 days-old commercial broilers. The results revealed that, the obtained four positive IBV isolates IBV-CH-EG-QAL-VVT.NRC-2021, IBV-CH-EG-ALEX-VVT.NRC-2021, IBV-CH-EG-GH-VVT.NRC.2021 and IBV-CH-EG-BH-VVT.NRC-2021 were all clustered in the distinct genotype I.23 lineage (GI.23) and phylogenetically within the Egyptian variant group the so-called Egyptian variant 2 (Egy/Var2) related to others previously registered in Egypt and neighboring countries. Furthermore, the 4 isolates were found to be pathogenic to broiler chickens with various mortalities of 30 and 40% along with respiratory and nephropathogenic lesions. These findings indicated the prevalence of the IBV variant strains in chicken flocks in Egypt with highly pathogenic features that heavily strikes the poultry industry with severe economic losses even in vaccinated flocks.

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