Nodavirus infection in freshwater ornamental fish, guppy, Poicelia reticulata--comparative characterization and pathogenicity studies.

Biochemical, genomic and serological studies were carried out to characterize a virus obtained from diseased guppy, Poicelia reticulata. The SDS-PAGE analysis of CsCl purified virus showed two distinct bands with molecular weight of 42 kDa and 110 kDa. A 1367 nucleotide region of the coat protein gene was sequenced, which includes one full open reading frame of 1017 nucleotides and a region of 350 nucleotides at the 3'end. The nucleotide identity of this strain with the nodavirus isolated from Epinephelus tauvina (Singapore strain) is 98% and with other strains of fish nodaviruses the identity is more than 75%. Western blot analysis using rabbit antisera raised against the nodavirus from marine fish, E. tauvina confirmed its antigenic similarity to the marine nodavirus isolate. Asymptomatic infection in guppy fry was observed following experimental infection with this virus and the marine nodavirus isolate (Singapore strain) implying the spread of virus from marine fish to freshwater fish. This report forms the first description of a nodavirus infection in freshwater fish.