Department of Fisheries and Wildlife, College of Agriculture and Natural Resources, Michigan State University, East Lansing, Michigan, USA.
Department of Fisheries and Wildlife, Quantitative Fisheries Center, Michigan State University, East Lansing, Michigan, USA.
J Fish Dis. 2022 Jul;45(7):1023-1032. doi: 10.1111/jfd.13626. Epub 2022 Apr 25.
Lake whitefish (Coregonus clupeaformis; LWF) is an economically and ecologically valuable native species to the Great Lakes, but recent declines in their recruitment have generated significant concern about their future viability. Although studies have sought to identify factors contributing to declining recruitment, the potential role(s) of infectious diseases has not been thoroughly investigated. In 2018 and 2019, adult LWF were collected from Lakes Superior, Michigan, and Huron for clinical examination and bacteriological analyses. Herein, we describe the first isolation of Flavobacterium psychrophilum, aetiological agent of bacterial coldwater disease (BCWD) and rainbow trout fry syndrome (RTFS), from systemically infected adult LWF. Bacterial isolates were yellow-orange, Gram-negative, filamentous bacilli that were oxidase and catalase positive, and produced a flexirubin-type pigment in 3% potassium hydroxide. Isolate identity was confirmed via F. psychrophilum-specific PCR, and multilocus sequence typing revealed three new singleton sequence types (STs) that were distinct from all previously described F. psychrophilum STs. The prevalence of F. psychrophilum infections was 3.3, 1.7, and 0.0% in Lakes Superior, Michigan and Huron respectively. Findings illustrate the potential for F. psychrophilum to cause systemic infections in adult LWF and highlight the need for future studies to investigate the bacterium's potential role in declining LWF recruitment.
湖白鲑（Coregonus clupeaformis；LWF）是五大湖具有经济和生态价值的本地物种，但近年来其繁殖数量的下降引起了人们对其未来生存能力的极大关注。尽管已经有研究试图确定导致繁殖数量下降的因素，但传染病的潜在作用尚未得到彻底调查。2018 年和 2019 年，从密歇根州苏必利尔湖和休伦湖采集成年湖白鲑进行临床检查和细菌学分析。在此，我们描述了首次从系统感染的成年湖白鲑中分离出嗜冷杆菌，这是细菌性冷水病（BCWD）和虹鳟鱼苗综合征（RTFS）的病原体。细菌分离物呈黄色橙色，革兰氏阴性，丝状杆菌，氧化酶和触酶阳性，并在 3%氢氧化钾中产生 flexirubin 型色素。通过嗜冷杆菌特异性 PCR 确认分离物的身份，多位点序列分型显示三个新的单峰序列型（ST）与所有先前描述的嗜冷杆菌 ST 明显不同。嗜冷杆菌感染的流行率分别为苏必利尔湖、密歇根湖和休伦湖的 3.3%、1.7%和 0.0%。研究结果表明，嗜冷杆菌有可能导致成年湖白鲑的系统性感染，并强调需要进一步研究以调查该细菌在湖白鲑繁殖数量下降中的潜在作用。
