Phylogeny and genetic diversity of foot and mouth disease virus serotype Asia1 in India during 1964-2012

Foot and mouth disease virus (FMDV) serotype Asia1 was first identified in India in 1951 and since then causing significant proportion of FMD outbreaks in the country. In this paper genetic analysis of 219 isolates from India collected over a period of 48 years is described. Bayesian approach was used to estimate the date of divergence and evolutionary rate. Phylogenetic analysis indicated the circulation of three lineages (B, C and D) of which lineage B formed one genotype (I) which was prevalent during 1964-2000. Genotype II constituted by lineage C and D has been in circulation since 1979 till date. We observed dramatic form of clade turnover in serotype Asia1 in India. The time scale analysis indicated that the most recent common ancestors for Indian Asia1 strains existed around 77 years ago. The evolutionary rate of serotype Asia1 viruses (genotype II) from India was estimated at 5.871×10^-3 substitutions per site, per year. We observed several connections in our phylogeographic analysis indicating intense flow of virus among states. The antigenically critical sites were frequently substituted and positive selection was evident at many sites. Maximum likelihood analysis suggested that the strains circulating in the country since 2005 were different from the genetic groups (I-VII) identified earlier and designated here as Group VIII.