Alvin W. Smith

San Miguel Sea Lion Virus Isolation, Preliminary Characterization and Relationship to Vesicular Exanthema of Swine Virus

BETWEEN 1932 and 1954 there were repeated outbreaks of vesicular exanthema of swine (VES) in Californian swine herds, but since 1956 no cases have occurred in the United States and this has been attributed to a federal law which prohibited the feeding of raw garbage to swine1. The continuing importance of vesicular diseases of swine, however, is suggested by reports from Italy2, Hong Kong3, Austria, Poland and Britain (personal communication from A. H. Dariri, Plum Island Animal Disease Laboratory, 1973) of a vesicular syndrome in swine that could not be ascribed to foot and mouth disease virus (FMDV).

Leptospirosis Epizootic among California Sea Lions

A Leptospira species is suspected of being the etiological agenit in a recent epizootic among California sea lions. The disease was confined to subadult males of the species Zalophus c. californianus.

Characterization of Two New Serotypes of San Miguel Sea Lion Virus

Two new virus isolates, one from a California sea lion (Zalophus californianus californianus) and the other from a northern fur seal (Callorhinus ursinus) were partially characterized. Their physicochemical characteristics were similar to those of vesicular exanthema of swine virus (VESV) and San Miguel sea lion virus (SMSV). The virion morphology was in both instances typically calicivirus. On the basis of this and the serum cross-neutralization testing, these isolates were classed as two new types of SMSV and were designated serotypes SMSV-4 and SMSV-5.

A PRELIMINARY REPORT ON POTENTIALLY PATHOGENIC MICROBIOLOGICAL AGENTS RECENTLY ISOLATED FROM PINNIPEDS 1 2

Sea lions aborting on San Miguel Island, California, and fur seals on St. Paul Island, Alaska, were studied for the presence of infectious disease agents. Leptospira were isolated from both groups and may have been one cause of reproductive failure in both species. From a total of seven virus isolations made, one isolate from fur seals and two isolates from sea lions appear antigenically related by serum neutralization tests. In their host range, morphology, and physicochemical properties, the virus isolates are indistinguishable from Vesicular Exanthema of Swine Virus. Six mycoplasma isolations have been made but have not been fully characterized. A fungus, Scopulariopsis sp., isolated from three different sea lions, is the same genus that was repeatedly isolated from Navy divers during prolonged submergence studies.

PREVALENCE AND DISTRIBUTION OF FOUR SEROTYPES OF SMSV SERUM NEUTRALIZING ANTIBODIES IN WILD ANIMAL POPULATIONS1

Serum neutralizing antibodies to four serotypes of San Miguel Sea Lion Virus (SMSV) were demonstrated in a variety of marine and terrestrial species. These results show a wide geographic distribution of SMS viruses in the marine environment and indicate that certain terrestrial mammals have been infected with these so-called marine viruses. Evidence is presented supporting the theory that unidentified submammalian marine species are a reservoir for SMSV.

A new calicivirus isolated from a marine mammal.

SummaryA new serotype of calicivirus, designated as San Miguel sea lion virus type 6 (SMSV-6), was isolated from vesicular lesions on the flipper of a California sea lion pup. Serologic studies show that SMSV-6 neutralizing antibodies (SN) occur frequently among California sea lions and occasionally among northern fur seals. Feral swine, 1- to 6-week elephant seal pups and grey whales tested negative for SMSV-6 antibody.

CALICIVIRUS ANTIBODIES IN WILD FOX POPULATIONS1

Three populations of wild foxes were sampled for serum neutralizing antibody to calicivirus (San Miguel sea lion virus) types 1-5. Neutralizing activity was detected in serum from gray foxes resident on Santa Cruz Island, California, but not in Arctic foxes from Alaska. The results indicate that foxes may be naturally infected with caliciviruses, but their role in the transmission cycle is unknown.

Biophysical Comparisons of Calicivirus Serotypes Isolated from Pinnipeds

Biophysical properties of three new San Miquel sea lion virus isolates from pinnipeds were examined and compared with those of previously characterized serotypes. The caliciviruses showed an identical sedimentation rate of 183S in 5-20% sucrose. Buoyant densities in CsCl were in the range of 1.35-1.39 g/ml, with differences among the serotypes.

RENAL FIBROSARCOMA IN THE NORTHERN FUR SEAL

A 2-week-old northern fur seal female pup (Callorhinus ursinus) found dead in the Pribilof Islands had an irregular mass at the anterior pole of the right kidney. Histopathological examination revealed a fibrosarcoma.