Annual changes in predominant genotypes of rotavirus A detected in the feces of pigs in various developmental stages raised on a conventional farm

The goal of the present study was to improve understanding of the ecology of porcine rotavirus A (RVA) infection in pigs raised on a conventional farrow-to-finish farm. We collected 145 fecal samples over a 3-year period from suckling pigs and their dams, and pigs at 30, 60, 90, 120, and 150 days of age. Reverse transcriptase-polymerase chain reaction analysis revealed that 29 samples (20%) were positive for the viral VP7 gene. The detection rate of VP7 sequences was highest in 30-day-old pigs (67%), followed by suckling pigs (43%), lactating sows (17%), and 120-day-old pigs (7%). At least five different combinations of G and P genotypes were identified (G4P[13], G5P[6], G5P[13], G9P[6], and G9P[13]), and their appearance varied with time; three to four different combinations of G and P genotypes were detected in samples taken during each year, and predominant genotypes differed between suckling and 30-day-old pigs and changed annually. While the VP7 and VP4 sequences of isolates belonging to the same G or P genotype were highly similar with only two exceptions, some were combinations of different P or G genotypes, suggesting that gene reassortment occurred. Further, viral sequences carrying the same combinations of G and P genotypes were also identified in pigs of different ages in different years. Our findings here show a wide distribution of genetically diverse porcine RVA sequences that vary annually with respect to predominant genotype and according to developmental stage. These findings enhance our understanding of how RVA infections persist among farm-raised pigs.