| Compared the effects of different culture modes on prevention from the outbreak of WSSV in shrimp culture ponds. This paper also studied the effects of polyculture, salinity and pond's sediment on transmission and outbreak of WSSV.1. Salinity has a direct influence on the infection of WSSV of shrimp Penaeus vannamei by oral route. When the salinity is 20 ( At the salinity of 20), there are an outbreak of the disease with high mortality, at other salinity levels, the disease begins earlier and has a longer course.2. Though the Ruditapes philippinarum polyculture (In the polyculture of Penaeus vannamei and R. philippinarum), the stomach and foregut show positive in all parts of living R. philippinarum by dot-blot hybridization. R. philippinarum is not the hosts of WSSV. WSSV can transmit by suspended particles.The stomach and foregut of it can carry virus during filtering in the diseased water, and the other parts of living R. philippinarum may imbrue virus. So, The WSSV transmission of might exist during the shrimp culture.3. Effects between covering different sizes mash on the sediment with virus and treating sediment with virus by chlorine-containing disinfectant are also compared. ( To the sediment with virus, the methods of using different sizes mash covering on it and chlorine-containing disinfectant are also compared.).The results show that the latter is better.The correlation relationship of mash and the mortality is also found, when the DO is abundance, the influence of ammonia and nitrite on shrimp mortality is not significant.4. As the agent of WSSV, wild crabs and the resting eggs of zooplankton carrying virus can live through the winter in shrimp pond's sediment. The abrupt variation of seawater factors has a direct effect on the infection of shrimp. Aquaculture in cement ponds with seawater filtered by sand can prevent from the outbreak of WSSV. And enclosures farming can reduce probabilityof the infection of WSSV. |
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