Studies on Rickettsia-like organism disease of tropical marine pearl oyster, Pincada maxima and P. fucata Ⅳ.On histo-cytopathology of RLO disease

The histo-cytopathology of Rickettsialike organism (RLO)disease in marl-cultured pearl oyster, Pinctadu marima and P.Fucnzu with heavy mortalities were studied.Pathogenic Rickettsia-like organism has a marked pathogenicity for P.marimu and P.fucata and leads to similar pathological changes in two pearl oysters.At the histo-cytopathological levels, RLO disease prerented acute alterative inflammation and chronic hyperplastic inflammation.In the course of acute alteration, cytopathological effects in ROL-infected cells may result in cell disintegration, celllytic necrosis and cell degenerative necrosis, therefore the structures of tissues and organs.including mantle,gills,digestive tube,hepatopancreas,gonadial tube and small blood vessels throughout the body, of host were seriously destroyed.The destroyed degree of tissues and organs were associated with the numbers of RLO inclusions in infected host and the cytopathological effects of RLO infection were associated with the intracellular growth.by large numbers of RLO.Cell hyperplasy had two types including the hyperplasy of epithelia or endothelial cells and fibrohlast hyperplasy with fibrosis during chronic hyperplastic inflammation.According to the course of pathological changes RLO disease may be divided into two stages namely acute necrosis and chronic hyperplastic reparation.