Rotavirus Surveillance in Tap Water, Recycled Water, and Sewage Sludge in Thailand: A Longitudinal Study, 2007-2018.

The objective of this study was to describe the epidemiological and molecular surveillance of rotaviruses in tap water, recycled water, and sewage sludge in Thailand from 2007 to 2018. Three hundred and seventy tap water, 202 recycled water, and 72 sewage sludge samples were collected and processed to detect the rotavirus VP7 gene using RT-nested PCR. Rotavirus G genotypes were identified by DNA sequencing and phylogenetic analysis. The frequency of rotavirus detection was 0.54% of the tap water samples, 30.2% of the recycled water samples, and 50.0% of the sewage sludge samples. During the 12-year surveillance, G1 was prevalent most years and constantly predominant in recycled water and sewage sludge. G2 was identified in a tap water sample and in recycled water samples. G3 and G9 were observed in both recycled water and sewage sludge samples. The uncommon G6 rotavirus strain was identified in one recycled water sample. The rotavirus VP4 gene was detected in rotavirus strains with an identified G genotype using RT-multiplex nested PCR. The unusual P[6] genotype was the most frequently detected, followed by mixed P[6]/[4] and P[4] genotypes. Phylogenetic analysis of both G and P genotypes showed a close genetic relationship with sequences of human rotavirus strains. The high nucleotide identity of the rotavirus strains found in this study to human rotavirus strains suggests that the rotaviruses are derived from human source. These results represent useful epidemiological and molecular information for evaluating rotavirus distribution in water for consumption and irrigation, and in biosolids for agricultural application.