Overview of Vesicular Exanthema of Swine
(San Miguel sea lion virus disease)
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 band, and between the toes.
VES has been reported only in the USA, and not since 1959, but it remains of historic importance because of its clinical similarity to 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 USA.
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 cases, 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, vesicular exanthema of swine virus.
SMSV has also been isolated from vesicular lesions on marine mammals, seal meat, and perch-like fish in California. SMSV can produce lesions indistinguishable from those of VES in pigs, and the diverse pool of marine caliciviruses on the west coast of the USA 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 people with vesicular lesions, but the viruses are considered of minimal significance to public health.
In pigs, the clinical disease is indistinguishable from foot-and-mouth disease (see Foot-and-Mouth Disease), vesicular stomatitis (see Vesicular Stomatitis), and swine vesicular disease (see Swine Vesicular Disease).
Presumptive diagnosis in pigs is based on fever and the presence of typical vesicles, which break within 24–48 hr to form erosions. Diagnosis can be confirmed by ELISA, reverse-transcriptase PCR, complement-fixation tests, and electron microscopy on epithelial tissue, or after passage in swine tissue cultures. Serum neutralization tests and electron microscopy are also used.
Suspected cases of vesicular exanthema should be reported immediately to the appropriate authorities. Feeding of food scraps (garbage, swill) to pigs is illegal in many countries and can be done only under license and after cooking in the USA.