Molecular diagnosis and identification of avian influenza H5N8 in Pekin ducks

In Egypt, poultry farms are still experiencing pressure from the avian influenza viruses H5N1, H5N8, and H9N2, as well as economic losses from direct viral infection or sharing other diseases that increase respiratory complications. Despite the administration of multiple vaccines against these viruses, protective immunity cannot develop due to frequent virus mutation and changes due to immunological pressure or genetic mixing. In this study, a six-weeks-old flock of Pekin ducks showed sudden mortality without any symptoms, while the still survived birds showed depression, mild to severe respiratory and/or nervous symptoms and greenish diarrhea. The mortality rate reached 25.4% in two weeks. Postmortem lesion included severely congested organs, tracheitis, pneumonia, massive hemorrhages on coronary fat and heart muscles, thymic hyperplasia, necrosis, and hemorrhages on pancreas. Liver samples were H5 positive by PCR, and sequences identified two isolates with the accession numbers MW917155 and MW917160. The phylogenetic analysis and identity table of the obtained two isolates demonstrated their relationship to the clade 2.3.4.4.1, which includes Egyptian isolates from ducks, goose, and chickens from 2017 to 2019. Our results showed clinical manifestation as well as molecular techniques to support the diagnosis of ducks infected with the highly pathogenic avian influenza (HPAI) virus. Furthermore, our findings revealed a link between our isolates and earlier local and worldwide isolates, as well as a match with the vaccines used in Egypt. Further coordinated national investigations on the prevalence and variations of HPAI virus infection in Egyptian poultry farms as well as the efficacy of used vaccinations are advised.