EVOLUTIONARY ANALYSIS AND DETECTION OF POSITIVE SELECTION OF HEMAGGLUTININ AND NEURAMINIDASE GENES OF H5N1 AVIAN INFLUENZA FROM CHICKEN, DUCK AND GOOSE ACROSS ASIA

Abstract

Outbreaks of very high pathogenic avian influenza (H5N1) viruses are being reported in poultry in almost all countries including Asia. It has been reported that the spread is very fast and found that this virus is spreading in avian species since several years. In this study, the evidence of positive selection prominent to mutations was analyzed for the Hemagglutinin (HA) and Neuraminidase (NA) nucleotide sequences of H5N1 avian influenza from chicken, duck and goose across Asia. H5N1 avian influenza viruses are being a severe risk to the public health. Detection of positive selection sites in Hemagglutinin (HA) and Neuraminidase (NA) genes will help to trace the evolutionary path of these viruses from different poultry hosts. The positive/ diversifying selection (dN/dS (w) >1) was found to be showing significant signals in mutation of HA and NA genes and is evolving rapidly. The cumulative dN/dS (w) ratio was found ranging from 0.21 to 0.23 in HA gene and 0.16 to 0.25 in NA gene of Avian Influenza Virus from chicken, duck and goose. Furthermore, statistical Bayesian model methods were applied to interpret the genetic diversity of H5N1 strain, the evolutionary rates were ranging from 2.36x10-3 to 5.19x10-3 in HA gene and 2.28x10-3 to 6.25x10-3 in NA gene from chicken, duck and goose respectively, which revealed a rapid evolution in these viruses with respect to their genetic ancestor. Substitution rates and selection pressure in these three different hosts indicate that their dynamics of mutation and replication remain similar among the species studied and are important for evolution.