In 1996,a serious epizootic called white spot syndrome caused high mortality of cultivated Penaeus chinensis in Qingdao from June to August.Electron microscopy and reinfection test showed that Penaeus chinensis non occluded baculovirus (PcNOBV),the WSBV isolate from P.chinensis in China's Mainland,is the major causative agent of the epizootic.Meanwhile,reovirus like particles were observed in some of the diseased P.chinensis from the following sample tissues:gill,stomach,foregut and ovary.The reovirus like particles could sometimes be found infecting the same shrimp or the same tissue and even the same cell with PcNOBV.The viral particles were spherical with double shelled structure characteristic of reovirus without envelope and located in the cytoplasm of infected tissue cells.The diameter of the particle varies in different tissues ranging from 80 110nm.The size of inner core is 60nm.Based on its morphologic characteristics,the virus is assumed to be a reovirus and named Penaeus chinensis reo like virus(PcREO)temporally.It’s not clear currently what roles does it play in the occurrence of the epizootic.However,the facts of systemic infection of the virus in P.chinensis and dual infection with PcNOBV strongly indicate that PcREO might contribute to the occurrence of the epizootic.Further research is required to determine its characteristics of pathogenicity,biology and molecular biology.
