Vesicular exanthema of swine

Vesicular exanthema of swine is the best-documented example of ocean caliciviruses causing disease in terrestrial species. Unlike other similar viral diseases, VES does not infect cattle.

VES was first identified in California, USA from several incidents over the period 1932-35. Typically isolated populations of swine feed with raw garbage developed disease symptoms similar to but not foot-and-mouth disease. From 1936 through mid-December 1939, the disease disappeared and then abruptly reappeared, at times involving 40% of California swine herds. All these outbreaks in the 1930s and 1940s were shown to be caused by many distinct but related VES virus strains. The embargoes placed on raw California pork were successful in containing VES within California until 1952. That year, a passenger train between San Francisco and Chicago served California pork and discarded the raw pork trimmings into the garbage in Wyoming; the garbage was fed to swine subsequently redistributed by auction sale yard. Within 14 months, all major swine-growing areas in the United States (41 states) had reported VES. For the first time, the federal government activated eradication and quarantine measures against VES, including enforcement of federal laws requiring garbage to be cooked before it was fed to swine. By 1956, the last reported outbreak of VES had been contained, and the disease was said to have been eradicated. In 1959, VES was declared a foreign animal disease, even though it had never been reported outside the United States.

Control of VES is counted as a notable success story for regulatory veterinary medicine in the United States; within 24 years of its discovery as an entirely new disease, it was said to have been eradicated. However, its origins were not known but were said to have been de novo or from some unknown wild animal reservoir, which was extensively sought but not found. Swine were the only naturally infected host species; no evidence of human infection had been observed. It was only in 1972 that the same virus that caused classic VES was isolated from a population of San Miguel sea lions.