Thuong Khuong Van, Tuan Vo Van, Li Wenfeng, Sorgeloos Patrick, Bossier Peter, Nauwynck Hans
Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium.
Research institute for Aquaculture number 1, Dinhbang, Tuson, Bacninh, Vietnam.
Vet Res. 2016 Feb 29;47:39. doi: 10.1186/s13567-016-0321-5.
As earlier observations on peroral infectivity of WSSV in white-legged shrimp are conflicting, here, a standardized peroral intubation technique was used to examine (i) the role of the physical composition of the viral inoculum and (ii) the barrier function of the PM. In a first experiment, the infectivity of a WSSV stock was compared by determining the SID50 by intramuscular injection, peroral inoculation or via feeding. The following titers were obtained: 10(8.77) SID50/g by intramuscular injection, 10(1.23) SID50/g by peroral inoculation and 10(0.73) SID50/g by feeding. These results demonstrated that 10(7.54)-10(8.03) infectious virus is needed to infect shrimp by peroral inoculation and via feeding. Next, it was examined if damage of the PM may increase the susceptibility for WSSV by peroral route. The infectivity of a virus stock was tested upon peroral inoculation of shrimp with and without removal of the PM and compared with the infectivity upon intramuscular inoculation. The virus titers obtained upon intramuscular injection and peroral inoculation of shrimp with and without PM were 10(8.63), 10(1.13) and 10(1.53) SID50/mL, respectively. This experiment confirmed the need of 10(7.1)-10(7.5) infectious virus to infect shrimp via peroral route and showed that the removal of the PM slightly but not significantly (p > 0.05) facilitated the infection of shrimp. This study indicated that WSSV contaminated feed is poorly infectious via peroral route, whereas it is highly infectious when injected into shrimp. The PM plays a minor role as internal barrier of shrimp against WSSV infection.
由于之前关于白斑综合征病毒（WSSV）对白腿虾经口感染性的观察结果相互矛盾，在此，我们采用一种标准化的经口插管技术来研究：（i）病毒接种物物理组成的作用；（ii）围食膜（PM）的屏障功能。在第一个实验中，通过肌肉注射、经口接种或投喂来测定半数感染剂量（SID50），从而比较WSSV储备液的感染性。得到以下滴度：肌肉注射为10(8.77) SID50/g，经口接种为10(1.23) SID50/g，投喂为10(0.73) SID50/g。这些结果表明，经口接种和投喂感染虾需要10(7.54)-10(8.03)个感染性病毒。接下来，研究围食膜的损伤是否会增加虾经口感染WSSV的易感性。在有或没有去除围食膜的情况下，对虾进行经口接种，测试病毒储备液的感染性，并与肌肉接种后的感染性进行比较。有或没有围食膜的虾肌肉注射和经口接种后获得的病毒滴度分别为10(8.63)、10(1.13)和10(1.53) SID50/mL。该实验证实经口途径感染虾需要10(7.1)-10(7.5)个感染性病毒，并表明去除围食膜略微但不显著（p>0.05）地促进了虾的感染。这项研究表明，被WSSV污染的饲料经口途径感染性很差，而注入虾体内时则具有高度感染性。围食膜作为虾抵御WSSV感染的内部屏障作用较小。
