Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Key Laboratory of Maricultural Organism Disease Control, Ministry of Agriculture and Rural Affairs, Qingdao Key Laboratory of Mariculture Epidemiology and Biosecurity, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.
College of Marine Technology and Environment, Dalian Ocean University, Dalian, China.
Mol Genet Genomics. 2019 Aug;294(4):1007-1022. doi: 10.1007/s00438-019-01559-7. Epub 2019 Apr 9.
Acute hepatopancreatic necrosis disease (AHPND) is a recently discovered shrimp disease that has become a severe threat to global shrimp-farming industry. The causing agents of AHPND were identified as Vibrio parahaemolyticus and other vibrios harboring a plasmid encoding binary toxins PirA/PirB. However, the epidemiological involvement of environmental vibrios in AHPND is poorly understood. In this study, with an aim to reveal the possible transmission route of AHPND-causing V. parahaemolyticus, we sequenced and analyzed the genomes of four pairs of V. parahaemolyticus strains from four representative regions of shrimp farming in China, each including one strain isolated from diseased shrimp during an AHPND outbreak and one strain isolated from sediment before AHPND outbreaks. Our results showed that all the four shrimp-isolated and three of the sediment-isolated strains encode and secret PirA/PirB toxins and, therefore, are AHPND-causing strains. In silico multilocus sequence typing and high-resolution phylogenomic analysis based on single-nucleotide polymorphisms, as well as comparison of genomic loci in association with prophages and capsular polysaccharides (CPSs) consistently pointed to a close genetic relationship between the shrimp- and sediment-isolated strains obtained from the same region. In addition, our analyses revealed that the sequences associated with prophages, CPSs, and type VI secretion system-1 are highly divergent among strains from different regions, implying that these genes may play vital roles in environmental adaptation for AHPND-causing V. parahaemolyticus and thereby be potential targets for AHPND control. Summing up, this study provides the first direct evidence regarding the transmission route of AHPND-causing V. parahaemolyticus and underscores that V. parahaemolyticus in shrimp are most likely originated from local environment. The importance of environmental disinfection measures in shrimp farming was highlighted.
急性肝胰腺坏死病（AHPND）是一种新发现的虾病，已成为全球对虾养殖业的严重威胁。AHPND 的病原体已被确定为携带编码双毒素 PirA/PirB 质粒的副溶血弧菌和其他弧菌。然而，环境弧菌在 AHPND 中的流行病学作用尚不清楚。在这项研究中，我们旨在揭示携带 AHPND 的副溶血弧菌的可能传播途径，对来自中国四个对虾养殖代表性地区的四对副溶血弧菌菌株进行了测序和基因组分析，每对菌株包括一株在 AHPND 暴发期间从患病虾中分离的菌株和一株在 AHPND 暴发前从沉积物中分离的菌株。我们的结果表明，这四株虾分离株和三株沉积物分离株均编码并分泌 PirA/PirB 毒素，因此均为引起 AHPND 的菌株。基于单核苷酸多态性的基因座间多位序列分型和高分辨率基因组系统发育分析以及与噬菌体和荚膜多糖（CPSs）相关的基因组基因座比较，均表明来自同一地区的虾和沉积物分离株之间存在密切的遗传关系。此外，我们的分析表明，与噬菌体、CPSs 和 VI 型分泌系统-1 相关的序列在来自不同地区的菌株中高度分化，这表明这些基因可能在携带 AHPND 的副溶血弧菌的环境适应中发挥重要作用，因此可能是 AHPND 控制的潜在靶标。总之，本研究首次提供了携带 AHPND 的副溶血弧菌传播途径的直接证据，并强调了虾中携带 AHPND 的副溶血弧菌很可能来源于当地环境。研究强调了对虾养殖中环境消毒措施的重要性。
