Genetic Characterization of Serotypes A and Asia-1 Foot-and-mouth Disease Viruses in Balochistan, Pakistan, in 2011

Abstract

This study reports characterization of foot-and-mouth disease virus (FMDV) in samples collected from Balochistan, Pakistan. FMDV was detected by pan-FMDV real-time RT-PCR in 31 samples (epithelial and oral swabs) collected in 2011 from clinical suspect cases. Of these, 29 samples were serotyped by serotype-specific real-time RT-PCR assays and were confirmed by sequencing the VP1 coding region. Sixteen samples were found positive for serotype A and eight for serotype Asia-1, whereas five samples were found positive for both serotypes A and Asia-1. Two serotype A positive samples were found positive for two different strains of serotype A FMDV each. Phylogenetic analyses of serotype A FMDVs showed circulation of at least three different sublineages within the A-Iran05 lineage. These included two earlier reported sublineages, A-Iran05^HER-10 and A-Iran05^FAR-11 , and a new sublineage, designated here as A-Iran05^BAL-11 . This shows that viruses belonging to the A-Iran05 lineage are continuously evolving in the region. Viruses belonging to the A-Iran05^FAR-11 sublineage showed close identity with the viruses circulating in 2009 in Pakistan and Afghanistan. However, viruses belonging to the A-Iran05^HER-10 detected in Balochistan, Pakistan, showed close identity with the viruses circulating in Kyrgyzstan, Iran and Kazakhstan in 2011 and 2012, showing that viruses responsible for outbreak in these countries have a common origin. Serotype Asia-1 FMDVs reported in this study all belonged to the earlier reported Group-VII (Sindh-08), which is currently a dominant strain in the West Eurasian region. Detection of two different serotypes of FMDV or/and two different strains of the same serotype in one animal/sample shows complexity in occurrence of FMD in the region.

Keywords: foot-and-mouth disease; genetic diversity; molecular epidemiology; phylogenetic analysis; picornavirus.