Studies Of Environmental Stressors On Infectivity Of White Spot Syndrome Virus (WSSV) In Penaeid Shrimp

White spot syndrome virus (WSSV) has caused high mortality in many species of penaeid shrimp and other aquatic crustaceans throughout the world. There is a developing awareness that disease is an end of a complex interaction of the shrimp, its environment, and the pathogen itself. Indeed, there is considerable evidence to support links between environmental changes, diseases and a depression of the immune system (Pipe and Coles, 1995). A lot of studies have been done on its influence on growth and survival of cultured shrimps, however, in marine crustaceans, there is a scarcity of data to support the hypothesis that environmental changes induce a modification of the immune system, leading to an enhance susceptibility to infectious diseases. Salinity is one of the most basic parameters of the culture environment for marine shrimp. It may influence marine shrimp in a number of ways, including both ecological and physiological effects. Additionally, general animal health may determine how tolerant a species is to an environmental parameter such as salinity. In this article, by using immune responses (total haemocyte count and phenoleoxidase activity) as indicators of environmental stress in penaeid shrimp and dot-spot hybridization in detecting WSSV, the effect of different artificial infection methods, the effect of Heterosigma akashiwo to artificial infection under different treatments, the effect of the possibility of salinity variance as an inducement to the outbreak of white spot syndrome, are studied. As this may help us to understand and contribute the solution of some of the disease problems faced by shrimp farming. The results indicate that oral ingestion is a more efficient infection way than waterborne contact, and the distributions of virus in different tissues are also different under the two infection ways; Heterosigma akashiwo could delay the accumulation of virus in shrimp, thus lead to the relatively long live time under the virus infection; Salinity is an important environmental parameter affecting physiology, survival ofPenaeus japonicus, salinity variance can influence the immunocompetence of Penaeus japonicus, both increasing salinity and decreasing salinity will reduce its immunocompetence, penaeus japonicus will be more susceptible to pathogens such as WSSV under salinity stress, Salinity variation is one of the important inducements to the outbreak of white spot syndrome.