Birnaviruses of potential new serogroups isolated from tropical fish

Abstract

Over the last 10 years, viruses have been isolated from fish imported into Singapore and also from indigenous fish in Singapore. In 1993, the marble goby Oxyeleotris marmorata** underwent viral diagnostic investigation as there were frequent reports of high losses in that species after importation into Singapore. Viruses, identified as birnaviruses based on their size and a double-stranded RNA genome, were isolated in BF-2 cells from marble gobies which were imported from four other Asian countries. The viruses underwent serotyping using antisera against all nine serotypes in birnavirus Serogroup A and the single serotype in Serogroup B. The viruses did not cross react at all with any of the antisera. However, they were neutralised with an antiserum against a birnavirus isolated in 1991 from a single giant snakehead, Channa (=Ophicephalus) micropeltes, held in a Singapore farm. That birnavirus was also not neutralised by any birnavirus Serogroup A or B antisera, and Serogroup A or B viruses were not neutralised by the antiserum against the virus isolated from C. micropeltes. On that basis the marble goby and snakehead birnaviruses should be classified as members of a new birnavirus Serogroup.