Schmidt-Posthaus Heike, Ros Albert, Hirschi Regula, Schneider Ernst
Centre for Fish and Wildlife Health, Department of Infectious Diseases and Pathobiology, University of Berne, Laenggassstrasse 122, PO Box 8466, 3001 Berne, Switzerland.
Dis Aquat Organ. 2017 Mar 21;123(3):193-203. doi: 10.3354/dao03102.
Proliferative kidney disease (PKD) is an emerging disease threatening wild salmonid populations, with the myxozoan parasite Tetracapsuloides bryosalmonae as the causative agent. Species differences in parasite susceptibility and disease-induced mortality seem to exist. The aim of the present study was to compare incidence, pathology and mortality of PKD in grayling Thymallus thymallus and brown trout Salmo trutta under identical semi-natural conditions. Young-of-the-year grayling and brown trout, free of T. bryosalmonae, were jointly exposed in cage compartments in a river in the northeast of Switzerland during 3 summer months. Wild brown trout were caught by electrofishing near the cage, and PKD status was compared with that of caged animals. Cage-exposed grayling showed a PKD incidence of 1%, regardless of whether parasite infection was determined by means of real-time PCR or histopathology/immunohistochemistry. In contrast, PKD incidence of caged brown trout was 77%. This value was not significantly different to PKD prevalence of wild brown trout caught above and below the cage (60 and 91%, respectively). Mortality in grayling was significantly higher compared with that of brown trout (40 versus 23%); however, grayling mortality was not considered to be associated with PKD. Mortality of caged and infected brown trout was significantly higher than mortality of non-infected caged trout. Histopathology indicated an ongoing mostly acute or chronic active infection in brown trout, which survived until the end of exposure. The results suggest that grayling are less susceptible to infection with T. bryosalmonae compared with brown trout under the tested field conditions.
增殖性肾病（PKD）是一种正在出现的疾病，威胁着野生鲑科鱼类种群，其病原体为粘孢子虫寄生虫脑粘体虫（Tetracapsuloides bryosalmonae）。寄生虫易感性和疾病导致的死亡率似乎存在物种差异。本研究的目的是比较在相同的半自然条件下，河鲈（Thymallus thymallus）和褐鳟（Salmo trutta）中PKD的发病率、病理学和死亡率。当年的河鲈和褐鳟幼鱼，未感染脑粘体虫，在瑞士东北部一条河流的网箱隔舱中共同暴露3个夏季月。通过电捕鱼在网箱附近捕获野生褐鳟，并将其PKD状况与网箱中的动物进行比较。无论通过实时PCR还是组织病理学/免疫组织化学确定寄生虫感染情况，网箱中暴露的河鲈PKD发病率均为1%。相比之下，网箱中褐鳟的PKD发病率为77%。该值与在网箱上方和下方捕获的野生褐鳟的PKD患病率（分别为60%和91%）无显著差异。河鲈的死亡率显著高于褐鳟（40%对23%）；然而，河鲈的死亡率被认为与PKD无关。网箱中受感染褐鳟的死亡率显著高于未感染网箱鳟鱼的死亡率。组织病理学表明，褐鳟存在持续的大多为急性或慢性的活跃感染，这些褐鳟存活到暴露结束。结果表明，在测试的野外条件下，与褐鳟相比，河鲈对脑粘体虫感染的易感性较低。
