Swine vesicular disease (SVD) caused by enterovirus broke out for the first time in Japan in November, 1973. It occurred originally in a region producing breeding swine in Kanagawa Prefecture and prevailed up to the next month. Then an antibody survey was conducted to clarify the degree of infiltration of this virus among swine. Incidentally, antibody against SVD virus was detected in it from the sera of some swine which were considered to be free from the outbreak of SVD. These sera included those collected before the present outbreak and those harvested from swine produced and raised on farms in a region geographically apart from the site of the outbreak.
SVD virus is antigenically very well identical with Coxsackie virus B5 (CB-5), which is human enterovirus. Serum samples were collected from swine in the field and examined for the presence of antibody against CB-5 virus. Then studies were made on the relationship between this antibody and that against SVD virus with the following results.
1. Serum samples were collected from swine all over Japan at three points of time; that is, prior to the outbreak of SVD and 1 and 5 months after the termination of this outbreak. Serum positive for SVD antibody was detected at every point of time. The coefficient of correlation between the two types of antibody, however, was considerably low, or 0.34, 0.31, and 0.34 before and 1 and 5 months after the outbreak, respectively.
2. When serum samples were collected from swine apparently infected on farms involved in the outbreak of SVD and examined for the two types of antibody, there was a very high correlation (r=0.74-0.85) between the antibody titers of these two types.
3. The coefficient of correlation was low, or 0.44, in serum samples collected from swine manifesting only indistinct signs of infection and from those which had withstood the infection without showing any symptom on farms involved in the outbreak of SVD. It was also low, or 0.53, in serum samples (antibody titer, <44.0) harvested from swine which seemed to be in the ascending stage of antibody.
From these results, it was suggested that there might be an inapparent infection of swine in Japan with such type of virus as mentioned above which would not cause the production of vesicles, but that of low-titer antibody. As such virus, CB-5 virus, which was antigenically identical with SVD virus, or any other unknown virus was presumed to exist.
