Shero Michelle R, Burek-Huntington Kathy, McCorkell Robert, Nadler Steven A, Rzucidlo Caroline L, Klink Amy C, Hindle Allyson G, Burns Jennifer M, Johnson Shawn
Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Alaska Veterinary Pathology Services, Eagle River, AK, USA.
BMC Vet Res. 2025 Apr 29;21(1):300. doi: 10.1186/s12917-025-04740-w.
Marine mammals act as sentinel species, with top predators' overall health reflecting their ecosystem, integrated across multiple trophic levels. Yet apparently healthy wild animals may have significant subclinical pathology that goes undetected due to unknown medical histories. Marine mammals, particularly phocid seals, often suffer from heavy parasite burdens. While there are documented cases of severe respiratory infections resulting in complications during sedation, there have been no reports of gastrointestinal parasites contributing to poor outcomes during examinations requiring sedation or anesthesia. This report describes two unique presentations of high intestinal parasite loads that purportedly predisposed Weddell seals (Leptonychotes weddellii) to complications under sedation, and characterizes underlying pathology.
Two adult female Weddell seals exhibited prolonged apnea and vomiting while under intravenous sedation, that led to aspiration and mortality despite resuscitation attempts. Post-mortem examination revealed a severe Diphyllobothrium tapeworm impaction in the duodenum, with the parasitic mass causing a partial or complete obstruction. In both cases, the stomach was remarkably distended, suggesting the parasitic mass slowed gastric emptying. Both animals' stomachs contained a high parasite burden with roundworms embedded into the mucosa. Histological analysis identified underlying pathological conditions that were likely parasite related, including chronic pneumonia associated with lungworm infestations, reactive, depleted and fibrosed lymph nodes, granulomatous lymphadenitis and hepatitis. Further examination in one of the animals revealed severe gastritis and necrotizing duodenitis at the site of the cestode infection.
To our knowledge, this is the first description of a significant gastrointestinal parasitic impaction being linked to acute distress during sedation in a marine mammal. We provide an in-situ depiction of the severe cestode infection. It is noteworthy that both animals in this case study exhibited histopathology consistent with chronic inflammation across multiple organ systems. Whether animals were sufficiently immunocompromised that rapid parasite growth became unchecked, or whether the parasite infestation led to dysfunction in other organs remains unresolved. We discuss the potential for premedication with prokinetic agents that increase esophageal sphincter tone to mitigate complications in future late-summer Weddell seal handlings.
海洋哺乳动物作为指示物种，顶级捕食者的整体健康状况反映了其生态系统，涵盖多个营养级。然而，由于未知的病史，看似健康的野生动物可能存在未被发现的重大亚临床病理学问题。海洋哺乳动物，尤其是海豹科海豹，经常遭受严重的寄生虫感染。虽然有记录表明严重的呼吸道感染会在镇静过程中导致并发症，但尚无关于胃肠道寄生虫在需要镇静或麻醉的检查中导致不良后果的报道。本报告描述了两例独特的高肠道寄生虫负荷病例，据称这使威德尔海豹（Leptonychotes weddellii）在镇静状态下易出现并发症，并对潜在病理学特征进行了描述。
两只成年雌性威德尔海豹在静脉镇静过程中出现长时间呼吸暂停和呕吐，尽管进行了复苏尝试，但仍导致误吸和死亡。尸检发现十二指肠有严重的阔节裂头绦虫阻塞，寄生虫团块导致部分或完全阻塞。在这两个病例中，胃明显扩张，表明寄生虫团块减缓了胃排空。两只动物的胃中都有大量寄生虫负荷，蛔虫嵌入黏膜。组织学分析确定了可能与寄生虫相关的潜在病理状况，包括与肺线虫感染相关的慢性肺炎、反应性、消耗性和纤维化淋巴结、肉芽肿性淋巴结炎和肝炎。对其中一只动物的进一步检查发现绦虫感染部位有严重胃炎和坏死性十二指肠炎症。
据我们所知，这是首次描述海洋哺乳动物胃肠道严重寄生虫阻塞与镇静过程中的急性窘迫相关。我们提供了严重绦虫感染的原位描述。值得注意的是，本案例研究中的两只动物均表现出与多个器官系统慢性炎症一致的组织病理学特征。是动物免疫功能严重受损以至于寄生虫快速生长未受抑制，还是寄生虫感染导致其他器官功能障碍，仍未得到解决。我们讨论了在未来夏末处理威德尔海豹时使用增加食管括约肌张力的促动力药物进行预处理以减轻并发症的可能性。
