Molecular epidemiology and subgroup determination of bovine group A rotaviruses associated with diarrhea in dairy and beef calves.

The genome electropherotyping technique was used to examine group A rotaviral infections of diarrheic calves ranging from 1 to 85 days of age in 2 beef and 27 dairy herds. Coelectrophoresis studies demonstrated 38 distinct bovine group A rotavirus genome electropherotypes; all were long genome electropherotypes, and none had extra segments or unusual segment rearrangements. Genome electropherotypes in fecal specimens from diarrheic calves previously inoculated orally with a commercial, modified-live group A rotavirus vaccine differed from the vaccine genome electropherotype. Generally, when fecal specimens for genome electropherotyping were collected from two or more different calves within the same herd over a relatively short time, only one genome electropherotype was detected within a given herd. Different genome electropherotypes were detected in the same herd, however, when fecal specimens were obtained from different diarrheic calves over longer intervals (6 months or more). Twenty-three group A rotavirus strains with distinct genome electropherotypes, from diarrheic calves in 22 herds, were isolated and plaque purified in cell culture, and all were subgroup 1 group A rotaviruses. Non-group A rotavirus genome electropherotypes were not detected in 131 fecal specimens, negative for group A rotavirus, collected from diarrheic calves in 17 dairy herds.