Advances in Animal and Veterinary Sciences

Research Article
Adv. Anim. Vet. Sci. 7(s2): 96-106.
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Ahmed Mohamed El-Sadek Hegazy1, Abeer Fathy Ibrahim Hassan2, Hala Mohamed Nabil Tolba1*

1Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt; 2Veterinary Hospital, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.

Abstract | Avian influenza (AI) and Newcastle disease (ND) viruses are continuously affecting the Egyptian poultry industry in spite of intense vaccination schemes leading to sever economic losses. The aim of this study is to track the effect role of AIV and NDV infections in commercial layers between November 2017 and February 2019. In the present study, fifty tissue samples were collected from different layer flocks suffered from cyanosis in comb and wattles, variable respiratory manifestations and egg production problems and subjected for avian respiratory viruses screening using different diagnostic tools. Virus isolation was carried through inoculation of tissue homogenate into allantoic cavity of 9 days old SPF ECEs revealed that out of 50 samples, allantoic 35 samples were haemagglutination (HA) positive then and subjected for molecular identification based on real-time RT-PCR assay. Twenty-six allantoic fluid samples were for NDV with percentage of 74.28% while the remaining sixteen samples were positive for AIVs with percentage of 45.71% at which four samples were positive for H5 (4/16; 25%)positive, nine samples were H9 subtype positive (9/16; 56.25%) and 3 samples have mixed infection with H5 and H9 (3/16; 18.75%). Sequence analysis of the (HA and NA gene of two H5 isolates has a multi-basic amino acid motif at the cleavage site (321-PLREKRRKR/GLF-333), which is specific to highly pathogenic AIV. All H5N8 influenza isolates belonged to clade Russian like H5N8 reassortant. The H9N2 isolates had amino acid motif at the cleavage site (333-PARSSR/GLF-341), which is specific to Low Pathogenic AIV. Furthermore, sequencing and phylogenetic analysis of M gene of selected three NDV isolates showed all related to sub genotype VIIb field strain. Our obtained results revealed the co-circulation of two major avian respiratory viruses as avian influenza and Newcastle among layers.

Keywords | Avian Influenza virus, H5N8, H9N2, Newcastle disease virus, Layer flocks