Equine-like G3 rotavirus strains as predominant strains among children in Indonesia in 2015-2016

Rotavirus A (RVA) is a major cause of acute gastroenteritis in humans and animals worldwide. As a result of the segmented nature of the rotavirus genome, genetic reassortment commonly occurs. This study aims to clarify the genetic characteristics of RVAs circulating in Indonesia. From June 2015 through August 2016, stool samples were collected from 134 children aged <5 years (71 male and 63 female) with acute gastroenteritis who were inpatients at a private hospital in Surabaya, Indonesia. All stool samples were screened for RVA antigen using immunochromatography. Forty-two samples (31.3%, 42/134) were RVA antigen-positive. All RVA positive samples tested showed the unusual combinations of G3P[8] (n = 36) and G3P[6] (n = 3) with a short RNA pattern by G/P typing and polyacrylamide gel electrophoresis (PAGE). Whole genome analysis by next-generation sequencing (NGS) was performed for 11 strains to determine the RVA genotypes. Eleven rotavirus strains were found to carry a DS-like genetic backbone; nine strains showed a G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 genome constellation, which was recently reported in Australia, Hungary, Spain and Brazil; as well, two strains showed a G3-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2 genome constellation. The phylogenetic tree based on the VP7 gene showed that all 11 strains were classified as equine-like G3, which is genetically distinct and different in origin from typical human G3 strains. The phylogenetic tree based on the NSP4 gene showed that six strains were classified as bovine-like strain and the remaining five were classified as human strain. In conclusion, we identified the strains which are intergenogroup reassortants containing an equine-like G3 VP7, a P[8])/P[6] VP4, with a DS-1-like genetic backbone. These findings suggest that equine-like G3P[8] and P[6] RVA strains have been circulating in the Indonesian population for at least 1 year and probably longer, indicating a diversity of RVAs in this area.