Torres Patricio, Yera Hélène, Rubilar Alonso, Rouges Célia, Leyán Victor, Silva Ricardo
Instituto de Parasitología, Facultad de Medicina, Campus Isla Teja, Universidad Austral de Chile, Valdivia, Chile.
Parasitology-Mycology Laboratory, Dupuytren Universitary Hospital Center; Inserm U1094 IRD UMR270, University of Limoges, CHU Limoges, EpiMaCT-Epidemiology of Chronic Diseases in the Tropical Zone, Institute of Epidemiology and Tropical Neurology, Omega-Health 87000 Limoges, France.
J Parasitol. 2025 May 1;111(3):210-226. doi: 10.1645/24-71.
In the present study, we examined nonnative returning Chinook salmon caught between 2018 and 2023 in the Valdivia River basin, Chile, for endohelminth parasites. Zoonotic endohelminths were identified by morphological and molecular methods, based on a multiplex PCR or PCR and sequencing targeting the cytochrome c oxidase gene of diphyllobothriids or Ascaridoidea mitochondrial DNA. A total of 5,350 larvae of helminths were detected in the salmon, with 3.6% corresponding to the cestodes Dibothriocephalus latus and Dibothriocephalus dendriticus, with freshwater life cycles, and 96% to "Scolex pleuronectis," 0.2% to Hepatoxylon trichiuri, 0.1% to Nybelinia sp., and 0.1% to the nematode Phocanema cattani, all with a marine life cycle. All salmon had plerocercoids of Dibothriocephalus spp., with the highest percentage in the peritoneum and intestine. Only D. latus was identified in the muscles of 40% of salmon, with up to 7 larvae per host and a mean density of 0.1 larvae per 200 g. The present results indicate that most (63.6%) of the plerocercoids of Dibothriocephalus spp. can survive during the migration of Chinook salmon to the ocean and their return to freshwater. The sealworm P. cattani was found for the first time in Chinook salmon with a prevalence of 20% in the muscles. "Scolex pleuronectis" was abundant in the intestine and pyloric caeca, representing 96% of the identified endohelminths. One-third of the salmon had H. trichiuri in the body cavity, and Nybelinia sp. in the intestine wall. Plerocercoids of Dibothriocephalus spp. were mostly encapsulated and a few free in different organs. Histologically, the free larvae of Dibothriocephalus spp. were associated with an infiltrate of mononuclear and polymorphonuclear cells suggesting damage to their tegument. Larvae of Nybelinia sp. in the muscular layer of the intestine were surrounded by a thin capsule to which they were attached by the tegument; mononuclear and polymorphonuclear cells were observed outside the capsule and in some areas in contact with the larva. Plerocercoids of D. latus and Nybelinia sp. were associated with abundant mast cells in the intestinal wall. The presence of the zoonotic Dibothriocephalus spp. and P. cattani in returning salmon would increase their potential risk of transmission to the human population in the Valdivia River basin area. Similarly, salmon carcasses could facilitate the potential transmission of Dibothriocephalus spp. and P. cattani to wild and domestic mammals and wild birds.
在本研究中，我们检查了2018年至2023年期间在智利瓦尔迪维亚河流域捕获的洄游型奇努克鲑鱼体内的体内寄生虫。通过形态学和分子方法，基于多重PCR或针对双槽绦虫或蛔虫线粒体DNA的细胞色素c氧化酶基因的PCR及测序，鉴定了人畜共患的体内寄生虫。在鲑鱼体内共检测到5350条蠕虫幼虫，其中3.6%对应具有淡水生命周期的绦虫阔节裂头绦虫和树枝状裂头绦虫，96%对应“鲽鱼裂头蚴”，0.2%对应毛圆线虫，0.1%对应尼氏绦虫属，0.1%对应线虫卡氏海豹线虫，它们均具有海洋生命周期。所有鲑鱼体内都有裂头绦虫属的裂头蚴，在腹膜和肠道中的比例最高。仅在40%的鲑鱼肌肉中鉴定出阔节裂头绦虫，每个宿主最多有7条幼虫，平均密度为每200克0.1条幼虫。目前的结果表明，大多数（63.6%）裂头绦虫属的裂头蚴在奇努克鲑鱼洄游到海洋并返回淡水的过程中能够存活。海豹线虫卡氏海豹线虫首次在奇努克鲑鱼中被发现，在肌肉中的感染率为20%。“鲽鱼裂头蚴”在肠道和幽门盲囊中数量众多，占已鉴定体内寄生虫的96%。三分之一的鲑鱼体腔中有毛圆线虫，肠壁中有尼氏绦虫属。裂头绦虫属的裂头蚴大多被包裹，少数在不同器官中游离。组织学上，裂头绦虫属的游离幼虫与单核和多形核细胞浸润有关，提示其体表受损。肠道肌层中的尼氏绦虫属幼虫被一层薄囊包围，其体表附着在囊上；在囊外及与幼虫接触的一些区域观察到单核和多形核细胞。阔节裂头绦虫和尼氏绦虫属的裂头蚴与肠壁中大量的肥大细胞有关。洄游鲑鱼中存在人畜共患的裂头绦虫属和卡氏海豹线虫会增加它们在瓦尔迪维亚河流域地区传播给人类的潜在风险。同样，鲑鱼尸体可能会促进裂头绦虫属和卡氏海豹线虫向野生和家养哺乳动物以及野生鸟类的潜在传播。
