Molecular epidemiology of human astrovirus infections in Kolkata, India

The study is aimed to determine the seasonal distribution and clinical characteristics of astroviruses associated with acute watery diarrhoea among children in Kolkata and characterize them at the molecular level.Method of studyFaecal specimens of acute watery diarrhoea cases (n = 857) and non-diarrhoeic samples (n = 211) from the hospitals and a nearby field community were screened with IDEIA Astrovirus detection kit; astrovirus co-infections with rotavirus and/or picobirnavirus were detected by RNA-PAGE and silver staining. Further RT-PCR was carried out using specific primers, viz. Mon340 (+) and Mon348 (−) targeting a highly conserved domain of ORF1a (289 bp) of human astroviruses.ResultsAstrovirus infection was detected in 50 cases (50/857); astroviruses were detected mostly in children aged 6–12 months (50%); all non-diarrhoeic samples (n = 211) were negative for astrovirus. In 52% of astrovirus positive cases, the virus was detected as the sole agent; mixed infections were also detected with other diarrhoeic pathogens such as rotavirus (32%), picobirnavirus (2%), rotavirus and picobirnavirus (2%), picobirnavirus and Enterotoxigenic E. coli (ETEC) (2%), rotavirus and ETEC (2%), rotavirus and Enteroaggregative E. coli (EAEC) (2%), Enteropathogenic E. coli (EPEC) (2%), Shigella flexneri type 3a (2%) and Ascaris (2%). RT-PCR and sequencing of amplicons of astroviruses from Kolkata, with specific primers targeted to the conserved domain of ORF1a (289 bp) of the astrovirus genome, showed maximum homology to the astrovirus strain (“5–158”) from Seoul (98%).Results and ConclusionsClinical characteristics of the diarrhoeic children in Kolkata indicated that astrovirus infections were detected throughout the year and were associated with varying degree of dehydration and acute watery diarrhoea. In-depth molecular epidemiological surveillance of astroviruses in Kolkata is essential for better understanding of their overall genetic nature.