Group A Rotavirus Genotypes among Calf Herds in Southwest Nigeria and Implications for Human Rotavirus Vaccines’ Efficiency

Abstract

Rotaviruses have been widely reported to be associated with diarrhea in humans but fewer studies abound on other mammalian species. This prospective study was conducted to detect and characterize Rotaviruses from freely ranged migratory herds of cattle in Ekiti and Ondo states, Nigeria with a view to further expanding knowledge on rotaviruses, possible animal-human interspecies transmission and impacts on vaccine efficiency. By convenience sampling, between September 2014 and February 2015, stool samples from 120 calves, comprising settled and migratory herds of cattle were obtained and examined for group A rotaviruses using Certest® Quadruple Enzyme Immuno Assay. Rotavirus genomes were isolated by extraction from the positive samples, reverse transcribed and amplified by One-Step reverse transcription polymerase chain reaction (RT-PCR), and genotyped by semi-nested multiplex PCR. Representative PCR products of the genotyped samples were purified and sequenced using Sanger method. The generated query sequences were queried to the GenBank to retrieve similar sequences for pairwise alignment by ClustalW. Phylogenetic analyses by Neighbour-joining method were conducted at 1000 bootstrap replicates to obtain phylograms using MEGA 6 software. Fifteen samples (15/120: 12.5%) were positive for rotavirus. No statistically significant association existed between rotavirus infection and gender of the calves (χ2 = 0, df = 1, p = 1). Eight samples (8/15: 53.3%) were successfully genotyped where the G1, G5, G9, G10, G12, and P[6] were detected. Nucleotide Sequencing of the VP7 and VP4 genes of the genotyped samples confirmed strains G1P[6], G10P[6], and G12P[6] with 58% - 100% nucleotide identity within these viruses. Phylogenetic analysis revealed 2 possible transmissions from India and Honduras. Bovine rotaviruses were detected in freely ranged and settled calf herds in southwestern Nigeria at a rate of 12.5%. The strains identified were analysed to be group A rotavirus strains with potential interspecies transmission from human to calves and from bovine to humans. The detected mixed strains could eventually impact negatively on the effectiveness of available rotavirus vaccines over the prevailing serotypes in human infections.