Rotaviral Diarrhea in Pigs

Group A rotaviruses were first detected in pigs suffering from diarrhea in 1975. It is generally accepted that multiple rotavirus strains are present in most if not all conventional swine herds. Rotavirus infections are very prevalent and are commonly associated with diarrhea in suckling and weaned pigs. Early studies also demonstrated that porcine rotaviruses are physically and serologically similar to rotaviruses recovered from other host species including humans. Originally only rotaviruses sharing a common group A antigen were identified in swine. In 1980, viruses that resembled rotaviruses in physical appearance, size, and biochemical composition were detected using electron microscopy on fecal samples from diarrheic pigs. However, these rotaviruses were serologically different (did not share similar group A rotavirus determinants) from the previously identified conventional group A rotaviruses and hence did not react in diagnostic tests commonly used to detect group A rotavirus. These non-group A rotaviruses that have been referred to by a number of names including pararotaviruses, rotavirus-like viruses, antigenically distinct rotaviruses, and atypical or novel rotaviruses are now classified as groups B and C rotaviruses. Within a rotavirus group (A,B,C,E), the group members share similar viral determinants or antigens and thus cross-react with one another in various serologic or diagnostic tests. However there is no crossreactivity or cross-protection among the different groups of rotavirus, so vaccines for group A rotavirus do not cross-protect against group C rotavirus, etc. Antibodies against both group A and C rotaviruses are found in nearly 100% of pigs as they reach market weight. Detection of group C rotavirus is much more common (up to 56%) in nursing pigs (<7 days of age) while group A rotavirus was detected more commonly (up to 51%) in post-weaning pigs (21-35 days of age). Groups B, C and E rotaviruses are also associated with diarrhea in swine. Serologic surveys have indicated that antibodies to non-group A rotaviruses belonging to groups B,C and E are common in most swine populations. Some human group A, B and C rotavirus strains are of suspected animal origin (porcine, bovine, rodents).