Instability of human rotavirus G genotypes circulating in a rural area of Bangladesh.

A total of 280 fecal specimens from patients with acute gastroenteritis attending one rural hospital (Dharmapasha health complex, Sunamgonj) in Bangladesh from August 2004 to May 2006 were tested for rotavirus by Polyacrylamide Gel Electrophoresis (PAGE). The diversity of rotavirus was investigated using electropherotyping and reverse transcription-PCR amplification of the VP7 and VP4 genes. The electrophoretic patterns of dsRNA of rotavirus showed 9 different migrations (6 long and 3 short) by PAGE. In the year 2004-2006, group A rotavirus was detected in 112 out of 280(40.0%) specimens. G and P genotyping was performed among the 46 representative positive specimens, 20(43.5%) were emerging strain G9P[8], which were associated with VP6 genotype II (subgroup II), and NSP4 genotype B, followed by 16(34.8%) G2P[4], 8(17.4%) G1P[8] and 2(4.4%) G4P[8] strains. G9P[8] was found to be the most predominant strain in 2004, but the prevalence rate abruptly decreased during the period 2005-2006. In addition G2P[4] was the most prevalent strain in 2005 and 2006. G1P[8] was less prevalent in the study period then the previous years. Nucleotide Sequence identity of VP7 gene of G9 rotaviruses were higher than 99.4% with each other and all the G9 rotavirus strains in this study clustered in a single branch of the phylogenetic tree. Nucleotide sequence identity of complete VP4 gene of P[8] rotaviruses were more than 99.7% with each other and all the P[8] rotavirus strains in this study grouped in a single cluster suggesting recent emergence from a common ancestor. An important finding of this study is that the genetic profile of rotavirus is changing within very short period in Bangladesh and continued surveillance of the circulating strains is necessary to detect new strains or new variants which can escape immune protection induced by available vaccines.