'Candidatus Branchiomonas cysticola' is a common agent of epitheliocysts in seawater-farmed Atlantic salmon Salmo salar in Norway and Ireland

The prevalence and geographical distribution of the recently described endosymbiont 'Candidatus Branchiomonas cysticola' in Atlantic salmon Salmo salar gill epithelial cell cysts was investigated in seawater-farmed fish suffering proliferative gill inflammation (PGI). To this end, we devel...

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Bibliographic Details
Published in:Diseases of Aquatic Organisms
Main Authors: COLQUHOUN, Duncan J., MITCHELL, Susan O., TOENSHOFF, Elena R., FALK, Knut, HORN, Matthias, Steinum, Terje Marken, KVELLESTAD, Agnar
Other Authors: Norwegian Veterinary Institute ,, 100513
Format: Article in Journal/Newspaper
Language:English
Published: 2013
Subjects:
Veteriner Bilimleri
Tarımsal Bilimler
Su Ürünleri
BALIKÇILIK
Bitki ve Hayvan Bilimleri
Tarım ve Çevre Bilimleri (AGE)
VETERİNERLİK BİLİMLERİ
Sağlık Bilimleri
Norway
Atlantic salmon
Salmo salar
Online Access:https://hdl.handle.net/20.500.12627/32179
https://doi.org/10.3354/dao02563
Description
Summary:The prevalence and geographical distribution of the recently described endosymbiont 'Candidatus Branchiomonas cysticola' in Atlantic salmon Salmo salar gill epithelial cell cysts was investigated in seawater-farmed fish suffering proliferative gill inflammation (PGI). To this end, we developed a specific and sensitive real-time PCR assay for detection of the bacterium. 'Ca. B. cysticola' was found to be highly prevalent in Atlantic salmon gills sampled over 7 yr and from 17 geographically distant seawater locations in Norway and Ireland. 'Ca. B. cysticola' was found in significantly greater quantities in fish with large numbers of epitheliocysts, and fluorescence in situ hybridization confirmed its localisation within cysts. 'Ca. Piscichlamydia salmonis', a bacterium previously linked to epitheliocysts, was identified at relatively low levels of infection, apparently independent of epitheliocyst prevalence. These results suggest that 'Ca. B. cysticola' is the main cyst-forming bacterium in seawater-farmed Atlantic salmon in the studied countries. Our results also suggest a relationship between load of 'Ca. B. cysticola' and extent of pathological changes. Taken together with a previously described association between epitheliocyst load and severity of PGI in Norwegian salmon, the results could indicate a role for 'Ca. B. cysticola' in gill diseases such as PGI.

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