Pathogen Diagnosis And Epidemiolgy Of Penaeid Shrimp Viral Disease In Fuzhou

Viral diseases of penaeid shrimp have hindered the development of shrimp culture. In order to resolve the problem, we started with the major pathogen identification of the penaeid shrimp diseases in Fuzhou, and then we studied morphology, ultrastructural pathology and genome of the main pathogen, and epidemiology of the disease. Moreover, we compared the pathogen characterization with similar pathogens?in other regions, discussed its taxonomic class and named it PCBV. In order to identify the infective pathogen more exactly, we carefully cultivated 6 groups of different species of penaeid shrimp, which are Special Pathogen Free (SPF) shrimp. Then infective a pathogens were isolated and identified with these SPF shrimp. Finally, aaccording the results of experiments, we diagnosed the major disease of shrimp culture in Fuzhou as a viral disease which major pathogen is a non-occluded baculovirus. The intact virion is enclosed with two-layer-envelope, and it has a tail when it is observed by electronic microscope in negative stain. The diameter and length of virion are very different, and the most nucleocapsids are about 280-320 nm in length, and about 60-75 nm in diameter. But a few nucleocapsids are very long, and the longest is over 600 nm in length. Other nucleocapsids are very thin, and the thinnest is 40 nm in diameter. Virions assemble and mature in cytoplasm, and do not form any inclusion, but sometime they can form another special pathological iii ~H.A?i~M structure梠cclusion-body, OB. The viral genome is dsDNA, and its size is between 2 1-24 kbp. The virus is high virulent, and it can lead to 100% mortality of shrimp during a week under high temperature. It can infect various species of shrimp, including Penaeus monodon, Penaeus semisulcatus, Penaeus pencillatus and Metapenaeus ensis. The former three species of shrimps are infected easily, and their resistance of the disease is similar. But Metapenaeus ensis is more resistant to the disease than other three species of shrimps. When Metapenaeus ensis is infected by the virus, its course of disease is longer and its mortality is lower than others. Temperature could affect viral infectivity, and high temperature exacerbates disease, but there is not the threshold value of the lowest temperature to infect shrimp. The virus can be transmitted by birth and feed, but it cannot do it by water and excreta in general. However, favorable environment could delay disease and decrease mortality. According the results of PCR detection, the virus is different from PWSBV isolated from Tong抋n, Xiamen by The Third Institute of Oceanography, but it is similar in part of genome with HHNBV isolated from province Shandong by Yellow Sea Fisheries Research Institute and WSSV isolated from province Guangdong bye Zhongshan University. Although the virus is similar with other isolates in other regions, which have white spot symptom, in morphology, range of host, symptom etc, but it is very different from others in size of virion, distribution in host cell, size of the genome, etc. So, we think that it is a new virus of penaeid shrimp. According its special ultrastructural Iv...