The emergence of epitheliocystis in the upper Rhone region: evidence for Chlamydiae in wild and farmed salmonid populati
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ORIGINAL PAPER
The emergence of epitheliocystis in the upper Rhone region: evidence for Chlamydiae in wild and farmed salmonid populations Maricruz Guevara Soto1 · Beatriz Vidondo2 · Lloyd Vaughan3 · Helena M. B. Seth‑Smith4 · Lisbeth Nufer3 · Helmut Segner1 · Jean‑Francois Rubin5 · Heike Schmidt‑Posthaus1
Received: 3 November 2015 / Revised: 17 December 2015 / Accepted: 12 January 2016 © Springer-Verlag Berlin Heidelberg 2016
Abstract We present the first study comparing epitheliocystis in a wild and farmed salmonid in Europe. Sampling three tributaries to the Lake Geneva, including one from headwaters to river mouth, revealed an unequal distribution of epitheliocystis in brown trout (Salmo trutta). When evaluated histologically and comparing sites grouped as wild versus farm, the probability of finding infected trout is higher on farms. In contrast, the infection intensities, as estimated by the number of cysts per gill arch, were higher on average and showed maximum values in the wild trout. Sequence analysis showed the most common epitheliocystis agents were Candidatus Piscichlamydia salmonis, all clustering into a single clade, whereas Candidatus Clavichlamydia salmonicola sequences cluster in two closely related subspecies, of which one was mostly found in farmed fish and the other exclusively in wild brown trout, indicating that farms are unlikely to be the source of infections in wild trout. A detailed morphological analysis of cysts using transmission electron microscopy revealed Communicated by Erko Stackebrandt. * Heike Schmidt‑Posthaus [email protected] 1
Centre of Fish and Wildlife Health, Department of Infectious Diseases and Pathobiology, University of Bern, Bern, Switzerland
2
Institute of Veterinary Public Health, University of Bern, Bern, Switzerland
3
Institute of Veterinary Pathology, University of Zurich, Zurich, Switzerland
4
Functional Genomics Center Zurich, University of Zurich, Zurich, Switzerland
5
Fondation de la Maison de la Rivière, Tolochenaz, Switzerland
unique features illustrating the wide divergence existing between Ca. P. salmonis and Ca. C. salmonicola within the phylum Chlamydiae. Keywords Brown trout · Candidatus Piscichlamydia salmonis · Candidatus Clavichlamydia salmonicola · River · Farm
Introduction Epitheliocystis is a bacterial disease affecting more than 90 wild and farmed fish species worldwide, both in marine and freshwater (Paperna and Sabnai 1980; Lewis et al. 1992; Nowak and LaPatra 2006; Abowei and Briyani 2011; Stride et al. 2013a, b, 2014). Lesions occur on skin and gills in larval stages, but are largely restricted to gills in adult fish. Macroscopically, they present as white nodules which vary widely in size, from as large as 400 μm (Fehr et al. 2013) and readily visible to the naked eye, down to 10 μm (Schmidt-Posthaus et al. 2012) and only detectable histologically. Histologically, the infection was first described as intracellular cysts causing cell hypertrophy in epithelial cells of blue gills (Lepomis macrochirus) b
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