Studies On The Invasion Routes Of White Spot Syndrome Virus(WSSV) Into Shrimp

White spot syndrome virus (WSSV) is one of the main pathogens of penaeidshrimp diseases，which can cause considerable mortality in penaeid shrimp. WSSV isa large, enveloped, rod-shaped, double-stranded DNA virus, belonging to theNimaviridae family, Whispovirus genus. Except for the wide range of hosts incrustaceans, it has strong ability to trigger shrimp to death. Perhaps, the most crucialstage in the dynamics of virus infections is its mode of transmission. It has absolutelyproved that infection via intramuscular injection can lead shrimp to death. However,the mode of transmission in nature is still unknown. In order to the find the pathway,the work mainly includes two following aspects:(1) The invasion routes of WSSV into shrimp. In the present study, the initialinvasion routes of WSSV were monitored by fluorescence quantitative PCRtechnology (qPCR). The results revealed that the viruses were detected in the shrimphemolymph after mouth or gill exposure to high doses of WSSV, suggesting that theinvasion route is via gills or digestive tract but not via the cuticle containing chitin. Inaddition, we found that the shrimp were not infected when the concentration of thevirus in seawater was equal to or less than10~2virions/L. However, Shrimp wereinfected with equal to or more than10~3virions/L and viral nucleocapsids werenon-infectious to the shrimp. The results suggested that10~3virions/L is the lowestconcentration of the virus capable of causing an infection.(2) The entry of WSSV to shrimp with the form of intact virions. In our study,the pathways to the digestive tract and gills were monitored by frozen section andscan electron microscopy technology. The result suggests that WSSV entry the shrimpwith the form of intact virions.