Rotaviruses (RVs) are a major cause of acute viral gastroenteritis in young animals and children worldwide. Immunocompetent adults of different species become resistant to clinical disease due to post-infection immunity, immune system maturation and gut physiological changes. Of the 9 RV genogroups (A–I), RV A, B, and C (RVA, RVB, and RVC, respectively) are associated with diarrhea in piglets. Although discovered decades ago, porcine genogroup E RVs (RVE) are uncommon and their pathogenesis is not studied well. The presence of porcine RV H (RVH), a newly defined distinct genogroup, was recently confirmed in diarrheic pigs in Japan, Brazil, and the US. The complex epidemiology, pathogenicity and high genetic diversity of porcine RVAs are widely recognized and well-studied. More recent data show a significant genetic diversity based on the VP7 gene analysis of RVB and C strains in pigs. In this review, we will summarize previous and recent research to provide insights on historic and current prevalence and genetic diversity of porcine RVs in different geographic regions and production systems. We will also provide a brief overview of immune responses to porcine RVs, available control strategies and zoonotic potential of different RV genotypes. An improved understanding of the above parameters may lead to the development of more optimal strategies to manage RV diarrheal disease in swine and humans.

3%). Sequence analysis of partial VP7 genes of selected strains revealed that the G4 strains were closely related to one another (95%) and, to a lesser extent, to human (82 to 84%) and porcine (84 to 86%) G4 strains. The G11 strains detected shared identical VP7 gene sequences (100%) and were closely related to human (85 to 86%) and other porcine (83%) G11 strains. The G9 strains identified were closely related to one another and to human and other porcine strains (96 to 97%, 89 to 91%, and 89 to 91% nucleotide identities, respectively). The VP4 gene analysis revealed that P[7] strains were closely related to each other and to P[7] strains isolated from porcine, bovine, and panda samples (91 to 99%, 92 to 99% and 92 to 99%, respectively). The P[13] strains showed a higher diversity among themselves and with other porcine P[13] strains, ranging from 83% to 99% and from 82 to 97%, respectively. Our results demonstrate broad genetic heterogeneity of the RVA strains and suggest the possibility of genetic reassortment between different RVA genotypes within these farms.

Swine fecal samples collected from seven farms were screened for group C rotaviruses (RVCs) using a reverse transcription-polymerase chain reaction assay. A total of 380 samples were tested and 19.5% were positive. Of the 128 samples collected in 2012, 23.5% from nursing piglets and 8.5% from weaned piglets were RVC positive, with a higher RVC frequency in diarrheic (28.4%) than in non-diarrheic (6.6%) piglets. Two strains (RVC/Pig-wt/USA/RV0104/2011/G3PX and RVC/Pig-wt/USA/RV0143/2012/G6Px) from two different farms were characterized genetically to gain information on virus diversity based on full length sequences of the inner capsid VP6, enterotoxin NSP4 and the outer capsid VP7 and VP4 (partial for RV0104) genes. The VP6 gene of the two strains showed high (99%) nucleotide identity to one another, 84–91% identity to other porcine RVCstrains and 81–82% identity to human and bovine RVC strains. The NSP4 gene analysis revealed that RVC/Pig-wt/USA/RV0104/2011/G3PX and RVC/Pig-wt/USA/RV0143/2012/G6Px strains were not closely related to each other (87% identity), but shared higher identity with prototype RVC/Pig-wt/USA/Cowden/1980/G1Px strain (93% and 89%, respectively) and were more distantly related to human strains (72–76% identity). The VP7 gene analysis indicated that the two strains were distantly related to one another (72% identity). RVC/Pig-wt/USA/RV0143/2012/G6Px was most closely related to porcine RVC G6 strains (82–86% identity), whereas RVC/Pig-wt/USA/RV0104/2011/G3PX was most closely related to porcine HF (G3) strain (94% identity). Analysis of the full length nucleotide sequence of the VP4 gene revealed that RVC/Pig-wt/USA/RV0143/2012/G6Px was distantly related to porcine (75%), bovine (74%) and human (70%) strains. The deduced amino acid identities (69.5–75.6%) of VP4 between RVC/Pig-wt/USA/RV0143/2012/G6Px and other RVCs were low; hence, we propose that this strain comprises a new VP4 genotype. Our results indicate high genetic heterogeneity in RVCs genes and the concurrent co-circulation of different genotypes at the same time. Our findings are useful for the development of more accurate diagnostic tools, for basic research to understand gene function and to provide information for RVC diversity germane to vaccine development.