Partners and International Organizations
(English)
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BE, CY, CZ, DK, ES, FI, FR, GR, HU, IE, IL, IS, IT, MK, NL, NO, PL, SE, TR, UK
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Abstract
(English)
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Epitheliocystis is an infectious disease that affects a wide range of fish species. This includes not only food fish species of major economic importance such as salmon, rainbow trout, sea bass and sea bream, but also aquarium fish. Mortalities can be as high as 100%, the causative agents being related to a group of obligate intracellular bacteria already known as pathogens for other vertebrates, including humans, and known as chlamydiae. We have strong evidence that multiple chlamydial species can serve as the causative agents of epitheliocystis and could also demonstrate the infections were mostly plural in nature, and not due to a single species/strain. We proposed to develop in vitro (fish cell lines) and in vivo fish model (zebrafish) for studying the pathogenesis of Chlamydia-related 'epitheliocystis agents'. Furthermore, we continue our efforts to characterise the diversity of epithliocystis agents occurring in wild populations and in aquaculture. As reported last year, we first tested representative, established Chlamydiae strainsand could demonstrate that Waddlia chondrophila, Estrella lausannensis and Criblamydia sequanensis can establish infections in fish cell lines (Kebbi-Beghdadi et al., 2011; Fehr and Vaughan, unpublished). The studies with zebrafish were also successful, with bath incubation of Waddlia chondrophila and Criblamydia sequanensis leading to infections which we are now characterising in detail as a basis to explore the mechanisms of disease. In conclusion, the initial hypothesis drawn from our analysis of field epitheliocystis cases, that a diverse range of Chlamydiales could be pathogenic to fish cells and zebrafish has been supported. We were also fortunate identify three sources of (likely) recurrent infections to help maintain our efforts to isolate and cultivate strains directly from epitheliocystis inclusions. The first is the brown trout population in Switzerland, which is seasonally infected with Piscichlamydia and Clavochlamydia (Schmidt-Posthaus et al., 2011). The second source is in aquaculture facilities in Crete (Heraklion) where epitheliocystis causes severe mortalities in juvenile fish and the third is in pipefish, collected as part of studies into fish evolution and pathogenesis by the group of Tony Wilson, University of Zurich. All these efforts are either published or being prepared for publication and will form the basis for further research proposals to continue this work. Taken together this underlines once again the excellent opportunities offered by such a project within the setting of COST 867 for international collaboration and dissemination of information about this important aquaculture disease. In addition to recent reviews (Segner et al., 2011; Vaughan et al., 2012), a full report outlining the progress achieved by participation in COST 867 will be prepared on conclusion of this extension.
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