Active Outbreak Investigation, Isolation, and Molecular Characterization of Infectious Bronchitis Virus from Poultry Farms in Mekele and Bishoftu, Ethiopia
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Date
2024
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Addis Abeba University
Abstract
Avian Infectious Bronchitis (AIBV) is a highly contagious respiratory disease that affects the poultry industry globally. In Ethiopia, AIBV has been reported in both commercial and backyard chickens. The currently used vaccine effectiveness is limited due to a lack of cross-strain protection and outbreaks continue to make mitigating the disease in Ethiopia difficult. Therefore, the objectives of this study were to isolate, genomic, and phylogenetic analysis of circulating field AIBV. A cross-sectional study was conducted from November 2023 to May 2024 in Mekele (eighteen samples) and Bishoftu (thirty-one samples) cities. Twelve tissue and thirtyseven pooled swab samples were collected, and six out of forty-nine samples (five swab samples and one tissue sample) tested positive for AIBV using real-time PCR and conventional RT-PCR. The six samples propagated into embryonated eggs and exhibited characteristic AIBV lesions and mortality over five consecutive passages. All the six isolates originating from Bishoftu (n=4) and Mekele (n=2), were amplified targeting 466 bp of the S1 gene and 433 bp of the 3'UTR using one-step RT-PCR. The purified PCR product of the five isolates targeting the 3ˊUTR region was sequenced and analyzed using bioinformatics tools. The sequence alignment of Ethiopia’s five isolates revealed a similar sequence except for one isolate (Bishoftu/03/2024) showed a single nucleotide change (A: C) resulting in amino acid change Glutamine(Q) to Proline (P). The phylogenetic analysis demonstrated the genetic distance was lower
among the newly reported isolates (0.001) compared to the broader set of GenBank isolates (0.01), indicating a closer evolutionary relationship between the current local isolates and the Mexican isolates. Therefore, the findings identify genetically related local viral lineages that differ from strains used in imported vaccines. It also indicates that outbreaks were caused by infection with the IB virus which is creating a serious health risk in the poultry industry. Further research on the economic impact of AIB in poultry production, serotyping of circulating AIB viruses, and vaccine development based on the local isolates are recommended.
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Keywords
AIBV, Bishoftu, Chicken, Ethiopia, Isolation, Mekele, RT-PCR, Real-time, PCR, Sequencing, Phylogenetic analysis