Lymphoidal parvovirus-like particles in Australian penaeid prawns

Prawns in northern Queensland exhib~ted mult~nucleated g ~a n t cell formation in hypertrophied lymphoid organs. Mostly farmed Penaeus monodon, P, merguiensls and P esculentus were involved The transformation involved mild nuclear hypertrophy, marglnated chromatin and basophilic d a r k e n ~n g of increased cytoplasm In a multinucleate giant cell. Areas of transformation were d~screte, often bounded by elongated f~brocytes and sometimes fully encapsulated Basophilic inclusions occurred con~monly and eos~nophlhc lntranuclear inclus~ons rarely. These inclus~ons stalned for DNA with acndlne orange fluorescence. Associated lympho~dal changes was the presence of rounded F -l ~k e cells with basophilic, pyknolc nucleoli. Under the electron microscope, transformed lympho~dal cells d~splayed virus-hke parlcles of 18 to 20 nm diameter associated with inclusion b o d ~e s in the nucleus These particles were similar to a parvovlrus and named lymphoidal parvovirus-like (LP\/). Their similarities and relationship to hepatopancreatic parvovirus and infectious hypodermal and haematopoletic necrosis virus are discussed.