Genetic characterization of velogenic and lentogenic Newcastle disease viruses circulating among broiler chickens in Al-wadi Al-gadid Governorate, Egypt (2021)

Abstract

The present study aimed to investigate circulated Newcastle disease virus (NDV) genotypes, and avian influenza virus (AIV) co-infection among chicken flocks receiving NDV vaccines in Al-Wadi Al-Gadid governorate, Egypt. Ninety-eight clinical samples were collected from diseased chickens in 10 chicken farms during 2021. The virus propagation in embryonated chicken eggs was confirmed serologically by hemagglutination and hemagglutination inhibition tests and molecularly by RT-PCR using specific primers of the Fusion (F) gene and matrix gene of AIV. The results revealed that 15 isolates were NDV-positive, of them, four were AIV co-infected. The F genes amino acid sequence alignments for selected six isolates indicated two cleavage site motifs characteristic to lentogenic (1) and velogenic (5) strains. Also, specific amino acid substitutions in F1 and HRa regions correlated to fusion activity and neutralizing antibody production in the present velogenic isolates were observed. Phylogenetic analysis of the partial F gene sequences revealed the circulation of two genotypes, GII and GVII.1.1 (VIIj), in class II circulating among vaccinated chicken flocks in Al-Wadi Al-Gadid governorate. In addition, velogenic isolates are segregated into a distinct sub-clade from NDVs isolated in southern and northern Egypt. In conclusion, this is the first report on the genetic characterization of NDV among vaccinated chicken flocks in Al-Wadi Al-Gadid governorate. The current data will contribute to the NDV endemicity, genetic evolution, and biosecurity measurements to overcome NDV infection in this promising area for poultry production.