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Vesicular Exanthema of Swine

(San Miguel Sea Lion Virus Disease)


Peter R. Davies

, BVSc, PhD, University of Minnesota

Reviewed/Revised Aug 2021 | Modified Oct 2022

Vesicular exanthema of swine (VES) is an acute, highly infectious disease characterized by fever and formation of vesicles on the snout, oral mucosa, soles of the feet, coronary bands, and between the toes.

VES has been reported only in the US, and not since 1959, but it remains of historic importance because of its clinical similarity to foot-and-mouth disease Foot-and-Mouth Disease . Since 1972, San Miguel sea lion virus (SMSV), a virus indistinguishable from VES virus (VESV), and related caliciviruses have been isolated from marine mammals on the west coast of the US.

VESV, SMSV, and related viruses are members of the genus Vesivirus in the family Caliciviridae. Many immunologically distinct serotypes have been demonstrated (13 types of VESV from pigs and at least 16 types of SMSV from marine sources). In addition, a number of serotypes have been isolated from other host species and named accordingly: bovine, primate, cetacean, walrus, skunk, mink, rabbit, and reptile caliciviruses. In some instances, serotypes initially isolated in terrestrial animals (eg, reptile calicivirus) have subsequently been found in marine mammals. All of these viruses (except for SMSV-8, SMSV-12, and mink calicivirus) form a single virus species, VESV.

SMSV has also been isolated from vesicular lesions on marine mammals, seal meat samples, and perch-like fish in California. SMSV can cause lesions indistinguishable from those of VES in pigs; and the diverse pool of marine caliciviruses on the west coast of the US are a reservoir of potential swine pathogens. Two marine caliciviruses, serotype SMSV-5 and an unknown virus, have been isolated from vesicular lesions or throat washings of two human patients with vesicular lesions; however, these viruses are considered of minimal importance to public health.

A presumptive diagnosis in pigs is based on clinical signs, including fever and the presence of typical vesicles, which rupture within 24–48 hours to form skin erosions. Diagnosis can be confirmed by means of ELISA testing, reverse-transcriptase PCR assay, complement-fixation tests, and electron microscopic examination of epithelial tissue samples or tissue cultures. Serum neutralization tests have also been used.

Suspected cases of vesicular exanthema should be reported immediately to the appropriate authorities. Feeding of food scraps (e.g., garbage, swill, uncooked fish) to pigs is illegal in many countries and can be done in the US only after appropriate license and after cooking the scraps.

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