不同途径感染白斑综合征病毒 (WSSV) 对日本沼虾的致病性

Pathogenicity of white-spot syndrome virus in Macrobrachium nipponensis via different infection routes

摘要:

日本沼虾肉质鲜美、经济价值高，但其对白斑综合征病毒 (White spot syndrome virus, WSSV) 的易感性尚不明确。采用流行病学调查、感染试验和荧光定量PCR (qPCR) 等方法，研究了日本沼虾Macrobrachium nipponense对WSSV的易感性、感染发病率以及WSSV在其体内的增殖情况。结果表明：日本沼虾是WSSV的自然宿主，上海市附近省份地区120个样本的自然携带率为8.33%。日本沼虾可以通过注射、摄食、浸泡途径感染WSSV，10 d内累计感染率均为100%，累计死亡率分别为100%、75%和0%。其中注射途径感染日本沼虾，感染后5 d肌肉病毒含量达到感染后1 d的1 000倍，8 d死亡率达100%。用注射WSSV感染日本沼虾死亡率来测量病毒致死日本沼虾的半数致死剂量 (LD50)，2.71×105病毒粒子/μL能使日本沼虾死亡率达到50%以上。在养殖生产中，日本沼虾可以通过摄食感染WSSV的病虾或死虾而感染WSSV，也能通过浸泡在含WSSV的水体中而感染，并因此成为一种传播媒介，从而影响了WSSV的迅速传播与致病。

Abstract:

Macrobrachium nipponensis is delicious and has high economic value, but its susceptibility to white-spot syndrome virus (WSSV) is unknown. Susceptibility, morbidity, and multiplication of WSSV in M. nipponense were studied by epidemiological survey, infection experiment and qPCR. M. nipponense was the natural host of WSSV, and the natural carrying rate was about 8.33%. M. nipponense could be infected with WSSV via oral administration, muscle injection and immersion, and the cumulative infection rate of 10 d exposure was 100%, and the cumulative mortality rates were 100%, 75% and 0%, respectively. The infection of WSSV is fast by muscle injection. The virus content after 5 day’s injection is 1 000 times higher than that of the first day of infection, and the mortality rate reached 100% after 8 days. The median lethal dose (LD50) measured as the mortality of infected M. nipponense via injection indicated the LD50 in the concentration of WSSV of 2.71×105 virions/μL. In shrimp farming, M. nipponense can be infected by ingesting WSSV infected shrimp or dead shrimp, and also by soaking in WSSV-containing water and thus become a vector, consequently affecting the spread and pathogenicity of WSSV.