| Summary: | 博士 === 國立臺灣大學 === 動物學研究所 === 92 === 英文摘要
In this paper, there were two purposes in this paper, the first study was to analysis that co-infection of WSSV and IHHNV in Penaeus monodon. The second study was to assess accurately the WSSV DNA load after spawning by real-time PCR.
The detections of WSSV and IHHNV respectively in P. monodon brooders before and after spawning were by dot blot hybridization and single-step nested WSSV PCR. The data showed that for WSSV, the stress of spawning triggered replication of the virus. The replication rate of the virus were very fast after spawning, therefore the stress of spawning could trigger WSSV replication. But for IHHNV, the severity of the infection didn’t affect by spawning. The survival rate for WSSV infection only was low (12%), and the survival rate for IHHNV infection only was high (71%). And the survival rate for co-infection of WSSV and IHHNV was higher than that of WSSV infection only, that is 54%. This observation revealed that co-infection of WSSV and IHHNV was actually associated with a lower mortality rate of P. monodon brooders after spawning. The survival rate of brooders was not related to IHHNV infection level, this implies that IHHNV had an antagonist effect to WSSV infection. The WSSV infection level is a main factor to determine the fate of the infected brooders after spawning.
At various time points after spawning, the brooders were detected by real-time PCR analysis in spite of co-infection. When brooders are spawning, if their WSSV DNA copy numbers did not reach to the threshold value 103〜104copies/µg DNA, would delay the dead time after the spawning. In contract, brooders whose WSSV DNA copy numbers reach threshold value, dead soon after spawning. Therefore the WSSV replication should be triggered by spawning. Thus, three basic patterns could be determined Group Ⅰ had a relatively high initial virus load (approximately 8.49×102 ~ 7.58×103 copies/µg DNA), the virus invariably replicates rapidly up to the time of spawning. After spawning, the virus levels remain high and all of these shrimp die within a few hours. The other two groups both had similar initial virus loads (approximately 3.11×101~ 3.66×102 copies/µg DNA). As in group Ⅰ, the group Ⅱ virus replicates rapidly up to and beyond spawning and all the shrimp die soon after spawning. The group Ⅲ initial virus load was approximately 1.07×102~ 1.52×103 copies/µg DNA. After spawning, the virus load increased relatively less (approximately a 10-fold increase) and the shrimp survived well beyond spawning. In this study, we confirmed that the copy numbers of WSSV affected the survive rate of brooders after spawning by real-time PCR.
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