Molecular Characterization of Virulent Newcastle Disease Virus Isolates from Chickens during the 1998 NDV Outbreak in Kazakhstan

Newcastle disease virus (NDV) infects domesticated and wild birds throughout the world and has the possibility to cause outbreaks in chicken flocks in future. To assess the evolutionary characteristics of 10 NDV strains isolated from chickens in Kazakhstan during 1998 we investigated the phylogenetic relationships among these viruses and viruses described previously. For genotyping, fusion (F) gene phylogenetic analysis (nucleotide number 47-421) was performed using sequences of Kazakhstanian isolates as compared to sequences of selected NDV strains from GenBank. Phylogenetic analysis showed that all newly characterized strains belonged to the genetic group designated as VIIb. All strains possessed a virulent fusion cleavage site (RRQRR/F) belonging to velogenic or mesogenic pathotypes with intracerebral pathogenicity indexes (ICPI) varying from 1.05 to 1.87.