Characteristics of a new reovirus isolated from epizootic ulcerative syndrome infected snakehead fish

Epizootic ulcerative syndrome (EUS) has been infecting a wide range of fish es in the South and Southeast Asia for the last 2 decades. One reovirus-lik e agent (snakehead reovirus, SKRV), isolated from an EUS-infected snakehead fish and investigated in the present study, is the only reovirus so far is olated from an EUS-infected fish, SXRV was characterised by the presence of a double-stranded RNA genome with icosahedral symmetry and double capsid. The virus had an average size of 71 nm, a buoyant density of 1.36 g ml(-1) in CsCl and lacked a lipid-containing envelope, Apart from the above, the p resence of a segmented genome and structural proteins falling into 3 specif ic size classes confirmed that the virus belongs to the family Reoviridae. SKRV differed from aquareoviruses by the lack of a cytopathic effect (CPE) with syncitium formation and in the segmentation pattern of RNA genome. The resistance to pH (3.0 to 9.0) and heat treatment and inability to multiply in mammalian cell lines and haemagglutinate human 'O' red blood cells (RBC s) differentiated SKRV from the rest of the similar genera in the family Re oviridae. Serological comparison indicated the antigenic distinctness of th e isolate from selected American and European aquareoviruses, SKRV grew wel l in SSN-1 and SSN-3 cells at 25 to 30 degreesC but not in the most common Aquareovirus susceptible coldwater fish cell line -CHSE-214.