Sequence and phylogenetic analysis of virulent Newcastle disease virus isolates from Pakistan during 2009-2013 reveals circulation of new sub genotype.

Despite observing the standard bio-security measures at commercial poultry farms and extensive use of Newcastle disease vaccines, a new genotype VII-f of Newcastle disease virus (NDV) got introduced in Pakistan during 2011. In this regard 300 ND outbreaks recorded so far have resulted into huge losses of approximately USD 200 million during 2011-2013. A total of 33 NDV isolates recovered during 2009-2013 throughout Pakistan were characterized biologically and phylogenetically. The phylogenetic analysis revealed a new velogenic sub genotype VII-f circulating in commercial and domestic poultry along with the earlier reported sub genotype VII-b. Partial sequencing of Fusion gene revealed two types of cleavage site motifs; lentogenic (112)GRQGRL(117) and velogenic (112)RRQKRF(117) along with some point mutations indicative of genetic diversity. We report here a new sub genotype of virulent NDV circulating in commercial and backyard poultry in Pakistan and provide evidence for the possible genetic diversity which may be causing new NDV out breaks.