Recent molecular epidemiology of foot - and - mouth disease virus Asia 1

Introduction: Recently there has been an apparent increase of outbreaks due to foot-and-mouth disease (FMD) Asia 1. Spread has occurred into regions where this serotype has never or rarely been recorded People’s Republic of China (including Hong Kong), Russian Federation and Mongolia. To determine the relationships between FMD virus isolates from the various outbreaks, a phylogenetic study using complete VP1 gene sequences was undertaken. Materials and Methods: RNA extracted from either clinical samples or cell culture grown virus was subjected to RT-PCR using foot-and-mouth disease virus (FMDV)-specific primers targeting regions either side of the VP1 gene. The complete sequence of the VP1 gene was directly determined using standard automated sequencing techniques. Results: The VP1 region of more than 140 FMD Asia 1 viruses were amplified by RT-PCR and directly sequenced. Phylogenetic trees were generated by the Neighbor-joining method using the MEGA 3.1 software package. Recent virus isolates fell into six genetic groups. Discussion: FMDV serotype Asia 1 was recently responsible for multiple disease outbreaks throughout much of eastern Asia. Normally this serotype occurs in Southern and Southeast Asia and has been regularly reported in Afghanistan, India, Iran, Malaysia, Nepal, Pakistan and Thailand. However, at the end of 2004 through to 2006, in addition to some of these countries, outbreaks of Asia 1 were reported in several provinces or autonomous regions of the People’s Republic of China, Mongolia, Myanmar, several regions of eastern Russia, Tajikistan and Vietnam. Phylogenetic analysis of complete VP1 gene sequences from FMDV isolates responsible for these outbreaks showed that they were caused by viruses that belonged to six different lineages within the Asia 1 serotype. It appears from this study that some of these viruses have spread rapidly over large distances and are genetically very closely related to isolates collected 25 years ago in India.