A viral disease associated with mortalities in hatchery-reared postlarvae of the giant freshwater prawn Macrobrachium rosenbergii

During mortality outbreaks in hatchery-reared Macrobrachium rosenbergii pos tlarvae (PL) in Guadeloupe Island (French West Indies) during 1997, an asso ciated viral disease was discovered and the agent was subsequently isolated . The clinical signs presented by severely affected PL consisted essentiall y of an opaque whitish appearance of the abdomen. Histopathological changes in affected PL were characterized predominantly by pale to darkly basophil ic, often reticulated, cytoplasmic inclusions in the connective tissue cell s of most organs and tissues. The isolated virus was approximately 30 nm in diameter as observed with an electron microscope by negative staining. By its location, structure and size it could be related to different families of the small RNA cytoplasmic viruses such as the Picornaviridae or the Noda viridae. Its characterization is in progress.