Molecular characterization of group B rotavirus circulating in pigs from India: identification of a strain bearing a novel VP7 genotype, G21.

The occurrence of group B rotavirus (RVB) infections in pigs has been reported from different parts of world. However, such infection in the pig population maintained in Indian farms has not been investigated as yet. A total of 187 faecal specimens were collected from pigs reared in different pig farms/pigsties located in western and northern regions of India and tested for the presence of porcine RVB by amplification of the NSP2 gene using conventional RT-PCR. Nine specimens (4.8%) were shown to contain RVB RNA. N2 and N4 genotypes of NSP2 gene were detected in three and six RVB strains respectively. VP7 (G-type) and NSP5 (H-type) genes of selected six RVB strains were characterized to identify the genotypes. Multiple G (G7, G19 and G20) and H (H4 and H5) genotypes detected in the RVB strains indicated circulation of heterogeneous population of RVB strains in pigs of India. Additionally, one strain was proposed to belong to a novel RVB genotype designated as G21 on account of <80% identity of VP7 gene sequence with its counterpart in RVB strains from 20 established genotypes. Deduced amino acid sequence of VP7 gene also displayed the presence of seven unique substitutions in the strain. The study reports for the first time the occurrence of RVB infections in Indian pig herds and provides important epidemiological data useful for better understanding of ecology and evolution of porcine RVBs.