A SURVEY OF G6-SEROTYPE AND G10-SEROTYPE OF GROUP-A BOVINE ROTAVIRUSES FROM DIARRHEIC BEEF AND DAIRY CALVES USING MONOCLONAL-ANTIBODIES IN ELISA

Group A bovine rotaviruses (BRV) have been identified worldwide as a m ajor cause of diarrhea in the young of many species, including humans. Group A rotaviruses are classified into serotypes on the basis of the outer capsid proteins. VP7 (G types) and VP4 (P types). To date, ther e are 14 G types of group A rotaviruses, with G1, G6, G8, and G10 desc ribed for BRV isolates. In this study, G6- and G10-specific monoclonal antibodies (MAbs) were used in an enzyme-linked immunosorbent assay ( ELISA) for the G typing of BRV-positive stool samples from diarrheic b eef and dairy calves from South Dakota, Ohio, Michigan, Nebraska, and Washington, USA, and Ontario, Canada. ELISA plates were coated using a broadly reactive VP7 MAb (Common 60) or with G6- or G10-specific MAbs . BRV-positive fecal samples were diluted and added to duplicate wells , followed by the addition of polyclonal guinea pig anti-group A rotav irus serum as the secondary antibody. Several reference G6 and G10 BRV strains as well as other G types previously reported in cattle (G 1, G2, G3, G8) and BRV-negative samples were included as G type specifici ty and negative controls. From a total of 308 field samples analyzed, 79% (244/308) tested positive by the broadly reactive VP7 MAb; of thes e, 54% (131/244) were G6 positive, 14% (35/244) were G10 positive, 4% (9/244) were both G6 and G10 positive, and 28% (69/244) were G6 and G1 0 negative. The negative samples may represent additional or undefined serotypes. The 89 samples from South Dakota were further subdivided i nto samples from beef (n = 43) or dairy (n = 46) herds. G6 was more pr evalent in beef herd samples (67%) than in dairy herd samples (47.5%). In addition, dairy herds had higher percentages of G10-positive sampl es (17.5%), G6-G10 double positives (10%), and untypable samples (25%) than did beef herds, in which the prevalence of G10 positive samples was 5.5%, G6-G10 double positives was 5.5%, and untypable samples was 22%. Application of the serotype ELISA for the analysis of additional BRV samples will provide further epidemiologic data on the distributio n of BRV serotypes in beef or dairy cattle, an important consideration for the development of improved BRV vaccines.