Effects Of Environmental Factors And Vibrio On The Proliferation Of White Spot Syndrome Virus In L. Vannamei

White Spot Syndrome Virus (White spot syndrome virus, WSSV) was a hostwidely contagious, highly lethal virus of shrimp, seriously restricting the developmentof the world’s shrimp farming industry. WSSV in shrimp immunity levels in vivoproliferation not only with the shrimp, the virus itself, but also on environmentalfactors are closely related. Environmental factors not only affect the level of immunityof shrimp, but also affect the virulence of WSSV. Research the effected ofenvironmental factors on WSSV virulence and the proliferation of WSSV hasbecome an important means to solve the problem of WSSSV. In this paper, exploreedthe effected of Salinity, Ammonia, Nitrite-nitrogen gradual and mutations changed onpenaeus infected with WSSV and the proliferation of WSSV in penaeus, and exploreinfected with three kinds of Vibrio would affect the proliferation of white spotsyndrome virus in vivo penaeus under the different temperatures. The results were asfollows:1. There was significantly effect on the mortality of shrimp and WSSVproliferation in L. vannamei by the acute salinity changes from the initial salinity(23±1) to high salinity (32±1) and low salinity (14±1)(P<0.05), In the experiment ofsalinity gradient, the mortality in each group below18.9%at12h and had a deathpeak at48h, there was a significant difference (P<0.05) at72~96h, Therefore, salinitychange was influence on the disease resistance of shrimp,which caused WSSV rapidproliferation in vivo shrimp; For carrying WSSV shrimp, salinity changes will greatlyimprove the possibility of WSSV from latent infection into acute infection, so salinityis one of the key factors which caused WSSV from latent infection into acuteinfection.2. There was significantly effect on the mortality of shrimp and WSSVproliferation in L. vannamei by the acute concentration of ammonia nitroge changesfrom the initial concentration (0.05mg/L) to mid-concentration (1.25mg/L) and highconcentration (3.0mg/L)(P<0.05), In the experiment of concentration of ammonianitroge gradient, the mortality in each group13.3%（p>0.05）at24h and there was asignificant difference after48h(P<0.05). Therefore, the greater the change inconcentration of ammonia nitrogen for shrimp viral proliferation more significant, WSSV may be greater from a latent infection into acute infection, so the control ofwater in the ammonia content at low concentration levels is critical to prevent theoutbreak of WSS.3. Changes nitrite nitrogen concentration throughout the experiment, the firstWSSV infection experiments, the initial concentration of nitrite0.05mg/Lconcentration to10mg/L and a high concentration of20mg/L during the course ofgradual and abrupt Litopenaeus cumulative shrimp mortality and virus proliferationsignificantly (P<0.05). WSSV infection experiment, the initial concentration of nitrite0.05mg/L concentration to10mg/L and a high concentration of20mg/L gradients,mutations to24h shrimp mortality of less than12.2%,48h after the mutation groupfirst appeared mortality peak,72h~120h significant difference (P<0.05), andtherefore carry more sensitive shrimp WSSV change nitrite nitrogen concentration,causing WSSV from latent infection into acute infection. Nitrite nitrogen and gradualmutation results compared to nitrite mutations easier to improve shrimp on WSSVsusceptibility.4. The pathogenicity of Vibrio parahaemolyticus and WSSV under differenttemperatures: a temperature of19±1℃conditions, to the end of the experiment eachgroup carrying amount of cumulative mortality and virus were less than11.1%,1.2×103copies/g. Temperature of25±1℃conditions,48h~96h WSSV infectionalone mortality (63.3%) and co-infection group (62.2%) had no significantdifference, but12h~72h for all coinfected group of viruses carrying capacity(maximum value of2.5×102copies/g) was significantly lower than group WSSVinfection alone (1.9×105copies/g).96h coinfected group of viruses proliferate rapidly(5.7×104copies/g). Bacterial infection alone increases mortality increased with theconcentration (21.1%). Temperature of31±1℃under the conditions of mortalityand infection alone WSSV virus carrying amount (47.8%,2.2×104copies/g) wassignificantly lower than coinfected group (77.8%,3.9×105copies/g). Coinfectedgroup and individual bacterial infection group (33.3%) mortality rate increased withthe increase of the concentration of bacteria. Description coinfection (Vibrioparahaemolyticus and WSSV) and Vibrio parahaemolyticus infection alone virulenceof shrimp increased with increasing temperature, and the impact of co-infectionWSSV proliferation at different temperatures significantly.5. The pathogenicity of Vibrio anguillarum and WSSV under differenttemperatures: temperature of19±1℃conditions, to the end of each experimentalgroup and a virus carrying amount of cumulative mortality was lower than11.1%, 1.2×103copies/g. When the temperature is25±1℃when,48h~96h cumulativemortality WSSV infection alone coinfected group with significant difference (P<0.05),and save significant difference (P<0.05) between groups of different concentrations ofco-infection, the highest mortality rate of77.8%(coinfection concentration2.3×106cfu/ml group). When the temperature was31±1℃, the cumulative mortality in eachgroup began to increase in48h, mortality and virus co-infection group wassignificantly faster than the proliferation of WSSV infection alone group. Withprolonged infection, bacterial infection alone with concentration, shrimp deathaccelerated. Therefore, low temperatures, and WSSV and Vibrio anguillarumvirulence is not high, as the temperature increases, the combined virulence ofinfection increases with increasing temperature, the temperature can significantlyaffect Vibrio anguillarum and virulence of WSSV.6. The pathogenicity of Vibrio harveyi and WSSV under different temperatures: atemperature of19±1℃conditions throughout the experiment mortality are lower than8.9%, less than the carrying capacity of each group of viruses3.9×104copies/g.Temperature of25±1℃conditions, viral infection alone group (71.1%,1.9×105copies/g), and high concentrations of secondary infection group (77.8%,3.2×106copies/g) mortality and virus carrying amount of the interim from experiments startsignificantly higher than other groups (P<0.05), the death rate, a rapid increase in theamount of virus carriers. Infection with bacterial infection alone group concentrationis increased, the maximum value of (21.1%). Temperature of31±1℃conditionsWSSV infection alone group (47.8%,2.2×104copies/g) was significantly lower thanthe experimental mid secondary infection group (80.0%,6.1×106copies/g).Description Temperature WSSV and Vibrio harveyi virulence affect significantly thetemperature rises so that secondary infections and bacterial infection alone increasedvirulence, high and low temperatures inhibit virulence of WSSV.