Studies On The Effect Of Chemical Disinfectants On The Inactivation Of White Spot Syndrome Virus (WSSV) And Proliferation Of WSSV In Host

White spot syndrome virus（WSSV）belongs to the Whispovirus genus of theNimaviridae family. WSSV is a rod-shaped, non-occluded baculovirus with largedoubled-stranded DNA which can infect various shrimp such as penaeid shrimp andcrayfish. As a major pathogen in the shrimp farming, WSSV also has wide range ofhosts in crustacean with high infection and mortality rate. In this thesis, we discussedthe disinfection methods in the lab and shrimp farm via inactivation effect ofdisinfectant to WSSV. In addition, we indicate WSSV mainly invade and proliferate inwhich organ or tissue of shrimp by oral ingestion and the proliferation of WSSV inhematopoietic tissue cells of host and the titer of WSSV infection.(1) Select disinfectants. At present, the disinfectants are commonly used in shrimpfarming, including chloride, iodide, peroxide, oxidant such as potassiumpermanganate, which are mostly acting on the bacterial diseases. It has been reportedrarely in-depth study whether these disinfectants can disinfect WSSV and how theyaffect the infectivity of WSSV. In this paper, we choose povidone iodine, chlorinedioxide, hydrogen peroxide and potassium permanganate to treat WSSV virions. Inorder to define the effective concentration and time of disinfectant used in shrimpaquaculture that has inactivation effect to WSSV, we analyzed disinfectant effect onviral genomic DNA, structural protein and infectivity of WSSV virions. We found thatthe extent of the damage to viral structural proteins or genomic DNA has a negativecorrelation with the viral infectivity. The results revealed that the minimum effectiveconcentration of chlorine dioxide is50ppm and the reaction time is60minutes，itonly degrades viral structural proteins but also led to the loss of viral infectivity.WSSV was rendered non-infectious by25ppm and50ppm potassium permanganatetreatment within15min and5min, respectively. It can almost completely degrade theviral genomic DNA and structural protein, and the result of quantitative real-timePCR (qPCR) shows us that WSSV reduce infectivity to zero, as well these methoddoes not caused death of crayfish (Procambarus clakii). Comparatively, povidoneiodine and hydrogen peroxide has no disinfection effect on WSSV less than250ppm. Therefore, we consider chlorine dioxide and potassium permanganate are the properdisinfectant for WSSV.(2) The phase of WSSV proliferation in hematopoietic tissue cells. We used thefluorescence quantitative PCR to analysis the phase of WSSV genome replication inhematopoietic tissue cells, found the virus in cells increased in the12~24h postinfection. However, it decreased to a certain degree at36h, part of the virus releasedinto the medium. In the different multiplicities of infection （MOI）experiments, weextracted the total RNA of24h cells infected with the virus, analyzed virus genetranscription through the real-time RT-PCR and found that infection with MOI1000can make better infectious effect.(3) The target organ of WSSV initial invasion. In this study, we mimicked thenatural infective process of WSSV to Litopenaeus vannamei by feeding the shrimpwith muscle tissue of WSSV infected Procambarus clarkia. The viral loads in thedigest organs of challenged shrimp were determined by real-time PCR. The resultsshowed that from12h to24h post-infection, viral DNA copies in the stomachincreased over one hundred times, while there was only a three-fold increase inesophagus and a five-fold increase in midgut. The previous investigation throughscanning electronic microscopy indicated that WSSV had a much higher affinity tothe inner surface of stomach than to esophagus and midgut. The results indicate thatWSSV mainly invade and proliferate in stomach of shrimp, then infects other tissuesand organs through hemolymph circulation.