Swine vesicular disease viruses isolated from healthy pigs in non-epizootic period. II. Vesicular formation and virus multiplication in experimentally inoculated pigs.

An infection experiment was carried out on pigs with swine vesicular disease virus isolated from healthy pigs (SVDV-H). Inoculation was done by two routes, intradermal in the coronary band of the foot and oral. Observation was made on the formation of vesicles and their spread, the virus contents of serum, swab of the oral cavity, and feces, the vicissitude of neutralizing antibody titers, and the distribution of virus in the body. From its results the pathogenicity of virus was judged. In the pigs inoculated intradermally there was a difference in the extension of the area involved in vesicular formation between any two strains of virus. That is, vesicular formation was restricted to the site of inoculation, involved the site of inoculation and the sole of the hoof, or spread over the oral and nasal regions. In every pig, however, vesicles developed only for 2 approximately 5 days after inoculation. After that, repair progressed rapidly. Some strains caused viremia, which was mild. The virus was detected from the site of vesicular formation, but not from any organ. Neutralizing antibody began to be detected 3 days after inoculation. Its titer reached a plateau about 10 days later. In the pigs inoculated perorally, no vesicles were formed. The virus was only detected from the tonsils and the intestinal contents. These findings made it clear that SVDV-H was less pathogenic than swine vesicular disease virus isolated from diseased pigs.