Antigenic differences among pestiviruses.

Monoclonal antibody typing of pestiviruses, supplemented with genetic sequence comparisons, has shown that at least four antigenic clusters can be identified within the genus. One cluster represents "classic" bovine viral diarrhea strains, which also have been isolated occasionally from sheep and pigs, whereas a second group corresponds to classic swine fever (hog cholera) strains. A distinct group of "true" border disease isolates is found in sheep and has been isolated occasionally from swine. The fourth group is antigenically quite distinct form the others and has been isolated from sheep, pigs, and cattle. It includes recent American isolates from cases of acute severe hemorrhagic disease. The implications of these findings for diagnosis and control are discussed.