Faculty of Life Science and Biotechnology, Ningbo University, Ningbo, China.
J Fish Dis. 2011 Feb;34(2):131-8. doi: 10.1111/j.1365-2761.2010.01221.x.
Mud crab, Scylla serrata (Forskal), is the most commercially important marine crab species in China. In recent years, serious diseases have occurred in major mud crab culture regions in SE China. PCR detection of white spot syndrome virus (WSSV) in diseased mud crabs collected from Zhejiang Province during 2006-2008 showed a prevalence of 34.82%. To study the pathogenicity of WSSV to mud crab, healthy mud crabs were injected intramuscularly with serial 10-fold dilutions of a WSSV inoculum. The cumulative mortalities in groups challenged with 10⁻¹, 10⁻², 10⁻³ and 10⁻⁴ dilutions were 100%, 100%, 66.7% and 38.9% at 10 days post-injection, respectively. All moribund and dead mud crabs except the control group were positive for WSSV by PCR. Based on the viral load of the WSSV inoculum by quantitative real-time PCR, the median lethal dose (LD50) of WSSV in S. serrata was calculated as 1.10 × 10⁶ virus copies/crab, or 7.34 × 10³ virus copies g⁻¹ crab weight. The phenoloxidase, peroxidase and superoxide dismutase activities in haemolymph of WSSV-infected moribund crabs, were significantly lower than the control group, whereas alkaline phosphatase, glutamate-pyruvate transaminase and glutamic-oxaloacetic transaminase were higher than in the control group. WSSV was mainly distributed in gills, subcuticular epithelia, heart, intestine and stomach as shown by immunohistochemical analysis with Mabs against WSSV. The epithelial cells of infected gill showed hypertrophied nuclei with basophilic inclusions. Numerous bacilliform virus particles were observed in nuclei of infected gill cells by transmission electron microscopy. It is concluded that WSSV is a major pathogen of mud crab with high pathogenicity.
泥蟹，锯缘青蟹（ Forskal ），是中国最重要的商业性海洋蟹种。近年来，中国东南主要泥蟹养殖区发生了严重疾病。2006-2008 年期间，从浙江省采集的患病泥蟹中，通过 PCR 检测到白斑综合征病毒（ WSSV ）的流行率为 34.82%。为了研究 WSSV 对泥蟹的致病性，将 WSSV 接种物的连续 10 倍稀释液肌肉内注射给健康的泥蟹。在 10 天的攻毒后，用 10 ⁻¹ 、10 ⁻² 、10 ⁻³ 和 10 ⁻⁴ 稀释度攻毒的组的累积死亡率分别为 100%、100%、66.7%和 38.9%。除对照组外，所有濒死和死亡的泥蟹均通过 PCR 对 WSSV 呈阳性。基于定量实时 PCR 对 WSSV 接种物的病毒载量，锯缘青蟹的 WSSV 中位致死剂量（LD50 ）计算为 1.10×10 ⁶ 病毒拷贝/蟹，或 7.34×10 ³ 病毒拷贝 g ⁻¹ 蟹体重。在濒死的 WSSV 感染蟹的血淋巴中，酚氧化酶、过氧化物酶和超氧化物歧化酶的活性明显低于对照组，而碱性磷酸酶、谷氨酸-丙酮酸转氨酶和谷草转氨酶的活性则高于对照组。免疫组织化学分析表明，WSSV 主要分布在鳃、皮下上皮、心脏、肠和胃中，用针对 WSSV 的单抗进行分析。感染的鳃上皮细胞显示出核肥大，具有嗜碱性内含物。通过透射电子显微镜观察到感染的鳃细胞中的大量棒状病毒颗粒。综上所述，WSSV 是一种具有高致病性的泥蟹主要病原体。
