Vesicular exanthema of swine and San Miguel sea lion virus: experimental and field studies in otarid seals, feeding trials in swine

The naturally occurring disease caused by San Miguel sea lion virus in fur seals was characterized by small fluid-filled vesicles 1 to 25 mm in diameter on the nonhaired portions of the flippers. Early epithelial lesions contained multifocal sites of cell lysis. The resultant microvesicles enlarged and coalesced, forming grossly visible macrovesicles. Mature vesicles progressed to involve all layers of the epithelium but did not involve the underlying dermis. Intradermal inoculation of vesicular exanthema of swine virus type A48 or San Miguel sea lion virus type 2 into otarid (fur) seal pups caused plaque-like lesions around inoculated coronary bands. These swellings regressed without rupture by 96 hours postinoculation. One seal inoculated with San Miguel sea lion virus had a linear lingual erosion at ten days postinoculation. Virus was isolated from this site and from two uninoculated sites, the tonsil and testicle. Contact controls showed no evidence of infection. Virus was isolated in low titers from some sites of inoculation and draining lymph nodes from seals infected with vesicular exanthema of swine virus. Virus was recovered more easily, in higher titers, and from more tissues, from seals infected with San Miguel sea lion virus. Inoculated seals tested after four to ten days seroconverted. Feeding swine seal tissues from the inoculation experiments resulted in seroconversion in swine which were fed tissues from seals infected with vesicular exanthema of swine virus but not in those which were fed tissues from seals infected with San Miguel sea lion virus.