PATHOGENESIS OF SWINE VESICULAR DISEASE AFTER EXPOSURE OF PIGS TO AN INFECTED ENVIRONMENT

The pathogenesis of swine vesicular disease (SVD) has been studied fol lowing a natural route of infection. In two experiments groups of ten and eight pigs respectively were introduced into a stable contaminated with SVD virus. At various intervals after stable exposure, pigs were killed and the amount of virus was determined in serum, vesicles (if present), spleen, kidney, and in seven lymph glands representing vario us parts of the body. One day after the pigs were introduced into the stable, five out of eight pigs were viraemic and virus could be isolat ed from various tissues. At 2 d after introduction, three out of four pigs killed had vesicular lesions on the feet. The tonsils of all pigs killed between 1 to 7 d after introduction into the stable were virol ogically positive. Four days after introduction 50% of the pigs were s erologically positive and at 7 d all pigs had developed an antibody re sponse. This study shows that contact with a SVD virus contaminated en vironment can be equally as infectious as injection, or direct contact with SVD infected pigs, causing a rapid spread of the disease. Becaus e the tonsil was shown to be highly efficient in trapping and growing circulating virus, we recommend that in addition to serological examin ation, virus isolation from pig tonsils should be used to study the ep idemiology of SVD on farms where the infection is present.