Sahul Hameed A S, Bonami Jean-Robert
OIE Reference Laboratory for WTD, Department of Zoology, C. Abdul Hakeem College, Melvisharam, Vellore, 632 509 Tamil Nadu India.
Indian J Virol. 2012 Sep;23(2):134-40. doi: 10.1007/s13337-012-0087-y. Epub 2012 Aug 15.
Macrobrachium rosenbergii is the most important cultured freshwater prawn in the world and it is now farmed on a large scale in many countries. Generally, freshwater prawn is considered to be tolerant to diseases but a disease of viral origin is responsible for severe mortalities in larval, post-larval and juvenile stages of prawn. This viral infection namely white tail disease (WTD) was reported in the island of Guadeloupe in 1995 and later in Martinique (FrenchWest Indies) in Taiwan, the People's Republic of China, India, Thailand, Australia and Malaysia. Two viruses, Macrobrachium rosenbergii nodavirus (MrNV) and extra small virus-like particle (XSV) have been identified as causative agents of WTD. MrNV is a small icosahedral non-enveloped particle, 26-27 nm in diameter, identified in the cytoplasm of connective cells. XSV is also an icosahedral virus and 15 nm in diameter. Clinical signs observed in the infected animals include lethargy, opaqueness of the abdominal muscle, degeneration of the telson and uropods, and up to 100 % within 4 days. The available diagnostic methods to detect WTD include RT-PCR, dot-blot hybridization, in situ hybridization and ELISA. In experimental infection, these viruses caused 100 % mortality in post-larvae but failed to cause mortality in adult prawns. The reported hosts for these viruses include marine shrimp, Artemia and aquatic insects. Experiments were carried out to determine the possibility of vertical transmission of MrNV and XSV in M. rosenbergii. The results indicate that WTD may be transferred from infected brooders to their offspring during spawning. Replication of MrNV and XSV was investigated in apparently healthy C6/36 Aedes albopictus and SSN-1 cell lines. The results revealed that C6/36 and SSN-1cells were susceptible to these viruses. No work has been carried out on control and prevention of WTD and dsRNA against protein B2 produced RNAi that was able to functionally prevent and reduce mortality in WTD-infected redclaw crayfish.
罗氏沼虾是世界上最重要的养殖淡水虾，目前在许多国家都有大规模养殖。一般来说，淡水虾被认为对疾病有耐受性，但一种病毒性疾病在虾的幼体、后期幼体和幼虾阶段会导致严重死亡。这种病毒感染即白尾病（WTD）于1995年在瓜德罗普岛被报道，后来在马提尼克岛（法属西印度群岛）、中国台湾地区、中华人民共和国、印度、泰国、澳大利亚和马来西亚也有报道。两种病毒，罗氏沼虾诺达病毒（MrNV）和超小病毒样颗粒（XSV）已被确定为白尾病的病原体。MrNV是一种直径为26 - 27纳米的小型二十面体无包膜颗粒，在结缔组织细胞的细胞质中被发现。XSV也是一种二十面体病毒，直径为15纳米。在受感染动物中观察到的临床症状包括嗜睡、腹肌不透明、尾节和尾肢退化，并且在4天内死亡率可达100%。检测白尾病的现有诊断方法包括逆转录聚合酶链反应（RT-PCR）、斑点杂交、原位杂交和酶联免疫吸附测定（ELISA）。在实验感染中，这些病毒在后期幼体中导致100%的死亡率，但在成年虾中未能导致死亡。这些病毒的报道宿主包括海水虾、卤虫和水生昆虫。进行了实验以确定MrNV和XSV在罗氏沼虾中垂直传播的可能性。结果表明，白尾病可能在产卵期间从受感染的亲虾传播给它们的后代。在看似健康的白纹伊蚊C6/36和SSN-1细胞系中研究了MrNV和XSV的复制情况。结果显示C6/36和SSN-1细胞对这些病毒敏感。关于白尾病的控制和预防尚未开展任何工作，并且针对蛋白质B2产生的双链RNA（dsRNA）能够在功能上预防和降低白尾病感染的红螯螯虾的死亡率。
