Isolation and molecular characterization of velogenic Newcastle disease virus genotype VII.1.1 from commercial broilers and wild birds in Matrouh governorate, Egypt

Abstract

Velogenic Newcastle disease virus (vNDV) genotype VII.1.1 continues to cause severe economic losses in chicken flocks since its first detection in 2011. In this study, pooled samples from 36 diseased commercial broiler chicken flocks (vaccinated against ND) which were suspected to be infected with vNDV and 15 pooled cloacal swabs from 6 wild bird species in Matrouh governorate were tested for vNDV genotype VII.1.1. The results showed that 5 broiler samples (5/36 = 13.8%) and 2 cloacal swabs from wild marbled ducks (2/15 = 13.3%) were positive by real-time RT-PCR and 6/7 isolates had mixed viral infections. F gene partial sequence analysis of 2 vNDV isolates (broiler origin, with a GenBank accession No. OR778089) and (wild marbled duck origin, with a GenBank accession No. OR778090), revealed 97.9-100% similarity with previous Egyptian isolates of vNDV-VII.1.1. Furthermore, the intracerebral pathogenicity index score of an isolate of duck origin (no. 44) was 1.82. In conclusion, wild marbled ducks could be an important source of transmission of vNDV-VII.1.1 to commercial broiler flocks. Furthermore, the isolation of vNDV-VII.1.1 from vaccinated commercial broiler flocks necessitates the use of more genetically and antigenically matched vaccines for effective control of this devastating viral infection.