Investigation On The Infection Of White Spot Syndrome Virus(WSSV) From Different Areas In Macrobrachium Nipponense And Its Distribution In Different Tissues

Macrobrachium nipponense,commonly known as river prawn,green shrimp,etc.It is one of the most important local economic breeding species in China.Because of its delicious meat and high nutritional value,it is loved by the people.The breeding of M.nipponense is an important part of crustacean aquaculture in China.The main breeding provinces in China are Anhui,Hubei,Jiangsu.White spot syndrome virus(WSSV)is a serious viral disease that is one of the most harmful viruses in today’s shrimp farming industry.M nipponense is not susceptible to disease in the wild or in aquaculture production because of its strong disease resistance.However,in 2015,M.nipponense carrying WSSV were first discovered in Wuxi,although the main symptoms of white spot syndrome did not appear.However,due to the existence of WSSV,and nowadays,the breeding technology of M.nipponense is mainly polyculture.M.nipponense may become a medium for WSSV and pose a potential threat to other crustaceans.Therefore,the exploration of WSSV technology for non-destructive testing of M.nipponense is essential for the detection of WSSV of M.nipponense without symptoms.And it plays a great role in breeding and reducing losses.Through this technology,WSSV testing of M.nipponense in different regions and vivo organization can monitor the infection and infection of WSSV in some areas of China,and provide important information for the prevention and treatment of WSSV.The second step of M.nipponense and the tail muscle can be used as a sample for WSSV testing in actual testing.However,sampling the tail muscles will cause the sample to die,and using the second step as the sampling tissue will not cause the sample to die.And shrimp and crab have regenerative function,so the second step is used as the test sample and the tail muscle for comparative analysis.The number of samples in the second step and the tail muscles are both 40,both organizations are removed from the same sample,in the second step,the WSSV detection rate is 55%,and the tail muscle detection rate is 50%,and the detection results are corresponding,WSSV is detected in the tail muscle,and the corresponding second step can also detect WSSV.The results showed that the consistency of WSSV was detected in the second step and the tail muscle.and in the second step.WSSV expression was higher and easier to detect.The method used by WSSV in China is the national standard method.but the range of WSSV virus detectable by the national standard method is small,when the virus content is low,it is impossible to make an effective test by the national standard method.Therefore,by using qRT-PCR technique,it is compared with the national standard method.Dilute virus concentration to eight concentration gradients:1×101.0、1×102.0、1×103.0、1×104.0、1×105.0、1×106.0、1×107.0、1×108.0 copies/g,When the virus concentration is less than 1×103.0 copies/g.it can not be detected by the national standard method.But qRT-PCR can detect effective Ct values in these eight virus concentration gradients.Therefore,using the second step as the detection tissue,using the technique of qRT-PCR.a non-destructive method for infecting WSSV M.nipponense was established.QRT-PCR was used to detect WSSV in M.nipponense in Wuyuan County,Inner Mongolia,Bayanur,Urad Front Banner,Jingzhou,Hubei,Xuancheng,Anhui,and Taihu,Wuxi.Jiangsu.The test results showed that there were different degrees of infection in the four regions.The infection rate of Wuyuan County in Inner Mongolia Bayanur Urad Front Banner was 55.00%.the infection rate of Jingzhou in Hubei was 19.44%,and the infection rate in Anhui Xuancheng and Jiangsu Taihu District was 25.00%.The Ct value was substituted into the standard curve to calculate the virus copy number,according to the degree of infection from high to low:Inner Mongolia>Hubei>Taihu>Anhui.The average virus copy number of WSSV infected by M.nipponense in Inner Mongolia was 103.96 copies/g,103 70 copies/g in Hubei,103.59 copies/g in Taihu Lake,and 103.56 copies/g in Anhui.QRT-PCR was used to detect WSSV in embryos and different tissues.The results showed that in the M.nipponense infected with WSSV,the virus detection rate was greater than 90%with hepatopancreas(28/30.93.00%),brain(27/30.90.00%).muscle(27/30.90.00%).),abdominal nerve(27/30.90.00%),detection rate between 80%and 90%of heart(23/30,83.33%),intestinal(26/30.86.67%),ovary(23/30),83.33%).embryos(23/30,83.33%),the detection rate between 70%and 80%is gill(23/30,76.67%).Substituting the Ct value obtained by qRT-PCR into a standard curve,and Obtained virus copy number of each tissue,then perform SPSS statistical analysis,the results showed that there was significant difference between the intestine and sputum,ovary,brain and muscle(P<0.05).The difference between hepatopancreas and sputum,ovary and brain was significant(P<0.05).The ovary was significantly different from brain,abdominal nerve,intestine and hepatopancreas.P<0.05),muscle was significantly different from intestinal and hepatopancreas(P<0.05).The degree of WSSV infection is hepatopancreas>embry>intestinal>abdominal nerve>heart>brain>muscle>gill>ovary.The highest degree of infection of the hepatopancreas with the highest degree of infection was 104.35 copies/g,and the average number of copies of the virus carried by the least infected ovary was 103.71 copies/g.The average virus copy number of the embryos was 104.34 copies/g,the intestine was 104.31 copies/g,the ventral nerve was 104.02 copies/g,the heart was 103.97 copies/g,the brain was 103.89 copies/g,the muscle was 103.86 copies/g.the gill was 103.82 copies/g.