Phylogenomic analysis of bovine astrovirus expands the known repertoire of mamastrovirus genotypes in northern India

Bovine astrovirus (BoAstV) belongs to the family Astroviridae and the genus Mamastrovirus (MAstV). Phylogenomic analysis based on partial sequences of the RNA-dependent RNA polymerase (RdRp) gene has allowed BoAstV isolates to be classified into the genotypes MAstV-13, 24, 28–30, and 33–35. However, information about the clinical significance and molecular characteristics of BoAstV from India is restricted to a single study from western Maharashtra, India. In this study, using RT-PCR detection of a portion of the RdRp gene, we investigated the presence of BoAstV in 134 rectal swabs samples from diarrheic and non-diarrheic calves less than three months of age from four states of North India (Rajasthan, Uttar Pradesh, Himachal Pradesh, and Haryana). Of these, 31 (23.1%) samples tested positive for BoAstV, with a higher rate of positivity in calves less than one month of age (30%, 21/70) than in calves between 1 and 3 months of age (15.6%, 10/64). Phylogenetic analysis based on partial RdRp gene sequences revealed the circulation of four different genotypes (MAstV 28, MAstV-33, MAstV-35, and MAstV-3) in Haryana. To the best of our knowledge, this is the first report of the presence of bovine astrovirus in cattle and buffalo calves in North India and of genotype MAstV-3 in calves.