白斑综合症病毒(WSSV)感染对虾的途径及滴度研究

Studies on the invasion routes of white spot syndrome virus (WSSV) into shrimp and virus titer

本研究利用荧光定量PCR技术,开展了白斑综合征病毒(WSSV)感染途径及染病最低病毒浓度的研究.用病毒分别感染对虾的口腔、鳃、背部甲壳和腹部软壳24 h后,利用qPCR测定血液中的病毒拷贝数,结果显示病毒主要通过口腔和鳃入侵宿主,并通过血液循环进行全身感染,但病毒不能穿过对虾的体表引起感染.此外,将对虾分别放在含不同病毒粒子浓度(101、102、103、104、105个/dm3)或含核衣壳的海水中培养,发现当海水中病毒粒子浓度低于102个/dm3时,对虾没有感染病毒,当浓度达到103个/dm3以上时能引起对虾感染.结果暗示103个/dm3是引起对虾感染的最低病毒粒子浓度,而核衣壳则不具有感染性.

White spot syndrome virus （WSSV） is a major pathogen in shrimp that causes high mortality and huge economic losses in shrimp aquaculture. Previous studies have shown that shrimp can be infected by means of water-borne contact and oral ingestion. However, quantitative date are not available. In our studies, the initial invasion routes of WSSV were monitored by fluorescence quantitative PCR technology （qPCR）. In this study, firstly shrimp were infected by means of mouth, gill, dorsum, and abdomen for 24 h and then virus copies in hemolymph of WSSV-infected shrimp were detected by qPCR. The result suggested that the invasion route is via gills or digestive tract but the cuticle. Secondly, in order to find out the infection minimum concentra- tion of WSSV in seawater, infection trail was performed using various concentrations while the healthy specimen was serving as a negative control. Then the hemolymph of WSSV-infected shrimp were taken every day, each group contained 10 specimens, respectively. At the same time, shrimp were challenged with WSSV virions and nucleo- capsids（with 105 concentration, respectively） for 48 h so as to know the infectively of nucleocapid, while the healthy specimen was serving as a negative control. Virus copies in hemolymph of infected shrimp were detected by qPCR. The result showed that shrimp were infected with equal to or more than 103 virions/dm3 and viral nucleocap- sids were non-infectious to the shrimp. The results suggested that 103 virions/dm3 be the lowest concentration of the virus capable of causing an infection. We can conclude that the prime invasion route is via gills or digestive tract.