U.S. Geological Survey, Madison, WI.
The University of Tennessee, Knoxville, TN.
Vet Pathol. 2023 Sep;60(5):510-528. doi: 10.1177/03009858231171666. Epub 2023 May 25.
Freshwater mussels are one of the most imperiled groups of organisms in the world, and more than 30 species have gone extinct in the last century. While habitat alteration and destruction have contributed to the declines, the role of disease in mortality events is unclear. In an effort to involve veterinary pathologists in disease surveillance and the investigation of freshwater mussel mortality events, we provide information on the conservation status of unionids, sample collection and processing techniques, and unique and confounding anatomical and physiological differences. We review the published accounts of pathology and infectious agents described in freshwater mussels including neoplasms, viruses, bacteria, fungi, fungal-like agents, ciliated protists, Aspidogastrea, Digenea, Nematoda, Acari, Diptera, and Odonata. Of the identified infectious agents, a single viral disease, plague disease, that occurs only in cultured mussels is known to cause high mortality. Parasites including ciliates, trematodes, nematodes, mites, and insects may decrease host fitness, but are not known to cause mortality. Many of the published reports identify infectious agents at the light or ultrastructural microscopy level with no lesion or molecular characterization. Although metagenomic analyses provide sequence information for infectious agents, studies often fail to link the agents to tissue changes at the light or ultrastructural level or confirm their role in disease. Pathologists can bridge this gap between identification of infectious agents and confirmation of disease, participate in disease surveillance to ensure successful propagation programs necessary to restore decimated populations, and investigate mussel mortality events to document pathology and identify causality.
淡水贻贝是世界上受威胁最严重的生物之一，在上个世纪已经有 30 多种灭绝。尽管栖息地的改变和破坏是导致其数量减少的原因之一，但疾病在这些灭绝事件中的作用尚不清楚。为了让兽医病理学家参与疾病监测和淡水贻贝死亡事件的调查，我们提供了有关淡水贝类保护状况、样本采集和处理技术以及独特而复杂的解剖学和生理学差异的信息。我们回顾了已发表的有关淡水贻贝病理学和传染病的描述，包括肿瘤、病毒、细菌、真菌、真菌样生物、纤毛虫、扁形动物门、复殖吸虫、线虫、节肢动物门、蜱螨目、双翅目和蜻蜓目。在已确定的传染病中，只有一种病毒性疾病，即 plague disease，仅在养殖贻贝中发生，已知会导致高死亡率。寄生虫包括纤毛虫、吸虫、线虫、螨虫和昆虫可能会降低宿主的适应性，但不会导致死亡。许多已发表的报告仅在光镜或超微结构水平上鉴定了传染病，没有对病变或分子特征进行描述。尽管宏基因组分析为传染病提供了序列信息，但研究往往未能将这些病原体与光镜或超微结构水平的组织变化联系起来，也未能证实它们在疾病中的作用。病理学家可以弥合传染病鉴定和疾病确认之间的差距，参与疾病监测以确保成功开展繁殖计划，从而恢复已减少的种群，并调查贻贝死亡事件以记录病理学并确定病因。
