Molecular Identification of a Velogenic Newcastle Disease Virus Strain Isolated from Egypt

Abstract

Newcastle Disease Virus (NDV) is still a major concern for the Egyptian poultry industry in spite of the mass vaccination programs implemented from a long years ago. The current study aimed to carry out the molecular identification of surface glycoprotein genes of NDV field strain isolated from the Giza governorate, Egypt. Tracheae were collected from 10 broilers NDV-vaccinated chicken flocks (at least three samples from each flock) suffering from mild to moderate respiratory symptoms; with mortalities varying from 10-40% during October 2019. Only five samples showed HA positive activity after propagation in specific pathogen-free embryonated chicken eggs and only one sample was positive for Avian avulavirus 1 by real-time reverse transcription-PCR. Sequencing for the cleavage site of the F protein gene of the positive isolate showed the typical known sequence of velogenic NDV strains (112RRQKRF117). Phylogenetic analysis of both F and HN genes showed high similarity and close relation to Chinese strains of Genotype VII and more specifically subtype VIId, suggesting the role of migratory wild birds in NDV evolution in Egypt. In conclusion, further epidemiological and surveillance studies are strongly recommended to define the exact role of migratory wild birds in NDV evolution in Egypt.