Molecular detection of betanodaviruses from apparently healthy wild marine invertebrates

One hundred eighteen samples (21 species) of wild marine invertebrates were collected from western and southern coastal area of Korean Peninsula. Four of 78 (18 species) samples collected at Namhae (South) area were positive for nodavirus in nested PCR test. Of the 40 samples (5 species) collected at Hwanghae (West) areas, all samples were negative for nodavirus in both RT-PCR and nested PCR tests. Positive nested PCR results were obtained from the following species: Charybdis bimaculata Charybdid crab; Pandalus hypsinotus Southern humpback shrimp and Mytilus galloprovincialis Mediterranean mussel. Phylogenetic analysis based on the partial nucleotide sequence (177 bases) of the RNA2 coat protein gene showed that the four strains were highly homologous (100%) and closely related to that of the known betanodaviruses, redspotted grouper nervous necrosis virus (RGNNV). These results indicate that nodavirus is present from wild marine invertebrates in the southern coastal areas of Korean Peninsula. These subclinically infected marine invertebrates may constitute an inoculum source for betanodavirus infection and cause mortality in cultured fishes in Korea.