Gilles Breuil

Viral infection (picorna-like virus) associated with mass mortalities in hatchery-reared sea-bass (Dicentrarchus labrax) larvae and juveniles

Abstract Histopathological lesions of the central nervous system are described hatchery-reared larval seabass during mass mortalities. Lesions are consistent with an extensive vacuolation of the brain and retina, associated with intracytoplasmic inclusions, containing RNA as demonstrated with acridineorange epifluorescence. Electron microscope observations revealed numerous cytoplasmic, non-enveloped particles about 22–23 nm in diameter. Isopycnic centrifugation in a CsCl gradient produced iwo bands of virus particles showing buoyant densities of 1.30 to 1.34 g/cm 3 , respectively. Negatively stained preparations exhibited full and empty icosahedral particles about 26 nm in diameter from side to side and 29 nm from point to point. By their characteristics, these particles are closely related to the Picornaviridae family.

Viral infection associated with rotifer mortalities in mass culture

Abstract 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.