Viral infection associated with rotifer mortalities in mass culture

Viral lesions were observed in rotifers, Brachionus plicatilis, during their mass culture as living food for seabream and turbot larvae reared in a French experimental hatchery. Isolated and purified virions, called RBV, exhibiting a buoyant density of 1.29–1.30, were non-enveloped, icosahedral in shape, and about 60 nm in diameter. When observed in thin sections or negatively stained, they exhibited the morphological characters of the family Birnaviridae. Because one virus of this family (IPNV) is considered highly pathogenic for salmonid fishes, and one other of this type (SBV) has been associated with seabass larvae mortalities, the possibilities of transmission to fish fed with such infected rotifers is discussed.