Epidemiological Disclosing and Molecular Subtyping for the Highly Pathogenic Avian Influenza Viruses H5N8 in Commercial Broilers and Layer Chickens in some Egyptian Governorates

Document Type : Original Article


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


Highly pathogenic avian influenza virus (HPAIV) H5N8 is a serious and fatal respiratory viral disease with an increase in the series of outbreaks in poultry field since its first emergence in Egypt from 2016 till now. Oral and cloacal swabs pool were collected from Sixty domestic poultry flocks of commercial broilers and layer chickens in four Egyptian governorates during 2023 that suffered from classic clinical disease of HPAIV with various mortalities reached 70% during the surveillance period. Molecular analysis was employed to analyze HPAIV subtypes H5 and NA (N1 and N8) by reverse transcriptase polymerase chain reaction (RT-PCR) and further partial hemagglutinin (HA) gene sequencing was carried out also to four positive representative isolates. The results initially revealed the negativity of all tested samples to H5N1 subtype, while H5N8 genome was predominantly positive in 17 out of the 60 examined flocks with prevalence rate 28.3%. Furthermore, the sequencing and phylogenetic tools indicated that our H5N8 isolates were in a close proximity to the clade with the characteristic amino acid motif (PLREKRRKR/GLF) in the HA gene cleavage site which is representative for pathogenic AIV strains. This study concluded the prevalence and predominance of HPAIV H5N8 in the domestic poultry farms in Egypt even in immunized flocks with the strict need of regular monitoring and active surveillances to those circulated strains as well as re-evaluation of the prevention and control protocols and also the vaccination efficacy assessment to overcome such endemic disease.


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