Differences in pathogenicity and antigenicity among hog cholera virus strains.

Using antiserum against a particular strain of bovine viral diarrhea virus, the strains of hog cholera virus were divided into two groups, H and B, on the basis of the difference in the degree of neutralization. Group H consisted of strains reacting poorly in neutralization, and group B Consisted of strains reacting well with bovine viral diarrhea antiserum. Most of the strains of group H induced a typical clinical form of hog cholera in experimentally infected pigs. Inoculation of pigs with a strain of group B, however, resulted in a chronic type of illness. When immunized with bovine viral diarrhea virus, pigs succumbed to challenge with group H virus after showing clinical signs of hog cholera, but survived challenge with group B virus without manifesting any clinical sign.