Isolation and molecular characterization of Newcastle disease virus genotypes II and VIId in Egypt between 2011 and 2012

Abstract

The current study was conducted to isolate and characterize Newcastle disease virus (NDV) from recent outbreaks affecting poultry farms in Egypt between 2011 and 2012. Trachea, spleen, liver, proventriculus and caecal tonsils were collected from clinically infected NDV ten different vaccinated broiler farms in Fayoum, Behira and Giza Provinces. Inoculation of all the collected samples in 10-day-old embryonated chicken specific-pathogen-free eggs resulted in isolation of haemagglutinating agents in three samples. These haemagglutinating agents were confirmed as NDV by real-time reverse transcription polymerase chain reaction (rt RT-PCR) using matrix (M) gene-specific primers. The deduced amino acid sequences of the fusion protein revealed that one isolate possessed the motif ¹¹²RRQKRF¹¹⁷ at the cleavage site, indicating that this isolate is velogenic genotype, whereas the other two isolates carries the motif ¹¹²GRQGRL¹¹⁷ indicating they are lentogenic genotype. The phylogenetic analysis revealed that the velogenic genotype isolate clustered with published class II genotype VII sub genotype d NDVs and closely related to Middle East isolates, whereas the other two isolates clustered with published class II genotype II NDVs. The spread of velogenic genotype strain to Egypt via Middle Eastern countries is likely to be the source of infection.