Vesicular exanthema of swine and San Miguel sea lion virus.

San Miguel sea lion virus (SMSV), recently isolated from marine mammals, and vesicular exanthema of swine virus (VESV), which caused epizootics of vesicular exanthema of swine (VES) over a period of 24 years (1932 to 1956), may be the same virus. This finding is of particular interest because the source of the original VES epizootic was never identified, swine were the only known natural host of VESV, and VESV was thought to have been eradicated. The SMSV has been shown to be enzootic in 2 species of marine mammals found off the coast of California and to cause lesions in swine that are indistinguishable from those caused by VESV. Therefore, we should be alert to recognize situations in which swine might become exposed to SMSV and to consider SMSV in differential diagnoses of vesicular conditions.