Abstract

Caliciviruses are often divided into groups on the basis of whether they have been isolated from, or detected serologically in, ocean-dwelling or land-dwelling hosts. San Miguel sea lion viruses (SMSVs), and vesicular exanthema of swine viruses (VESVs) are given as examples of marine caliciviruses, while feline caliciviruses (FCVs), rabbit hemorrhagic disease virus (RHDV), and human enteric caliciviruses are given as examples of terrestrial caliciviruses. A hallmark characteristic of marine caliciviruses is their unique ability to infect and cause disease in a diverse array of animal species, both marine and terrestrial. Epidemiological evidence suggests that, irrespective of nomenclature, caliciviruses utilize marine animals as reservoirs in the maintenance and transmission of infection in nature. In the Spring of 1991, sera were collected from twenty adult female California sea lions (Zalophus californianus) on San Miguel Island, California. Microtiter serum neutralization assays were performed against 100 TCID₅₀ units of FCV F-9, which is a vaccine strain used world wide. Assays were run in Vero monkey kidney cells, and 50% endpoint values were calculated. Seventeen of the 20 sera tested neutralized the challenge virus at a serum dilution of 1:10 or greater. The average neutralization serum dilution for the 20 sera tested was 1:73. These data suggest that feline calicivirus is present in our oceans, and is surviving within, and spreading through, ocean reservoir populations.