Vesicular exanthema of swine.

Vesicular exanthema of swine (VES) was first recognized in 1932. At the time, eradication measures and, later, quarantine procedures were instituted and extension of the disease to surrounding farms appeared to have been prevented. Between 1932 and 1936, however, seemingly unrelated epizootics continued among swine herds being fed raw garbage. In 1936, VES disappeared only to reappear in 1939. The disease was contained within California until 1952, at which time it spread to all the major swine producing areas of the United States. The disease was eradicated in 1959, through the enforcement of laws prohibiting the feeding of raw garbage to swine. Other than the association with raw garbage, a reservoir for VES virus (VESV) was never found. In 1972, a virus isolated from California sea lions--and thus named the San Miguel sea lion virus (SMSV)--proved to be distinguishable from VESV. When SMSV was injected into swine, clinical signs of vesicular exanthema developed, leading to the conclusion that, for all practical purposes, SMSV and VESV were the same. To date, 5 species of marine mammals and 2 species of terrestrial mammals, including feral swine, have been shown to possess antibodies to 1 or more of the 4 distinct SMSV serotypes. Current evidence suggests that SMSV infections occur among both terrestrial and marine mammals inhabiting the California coastal zones. This and the practice of shipping frozen meats known to contain SMSV to mink ranches in Utah point to the possibility that domestic swine in the United States are occasionally being exposed to SMSV. Although marine mammals are a source of SMSV, the primary virus reservoir is thought to be 1 or more submammalian marine species common to the southern California coastline. Such a primary reservoir presumably is the source of a new SMSV serotypes infecting marine mammals and may have been the original source of the VESV serotypes that infected swine through the intermediary of raw garbage.