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Sea lice and the Salmo salar mucosal microbiome

Sea lice, copepod fish ectoparasites, are a major burden of disease on commercially reared salmon. The annual cost of infection is considered to be in excess of €300 million. Several louse species are implicated, principally Lepeoptheirus salmonis and members of genus Caligus. Sea lice feed on host mucus, skin and underlying tissue, causing lesions that precede secondary bacterial infections.

In two linked projects, we are examining the infection of L. salmonis and Caligus rogercresseyi in relation to the salmon commensal microbiome, throughout their lifecycle. We aim to evaluate microbiome dynamics prior to and during parasite attachment, throughout pre-adult and adult development in both wild and farmed fish. We are hoping to explore infestation density effects, immunochemistry of the mucous composition, host heath status and the ecological succession of opportunistic pathogens that accompany lesion formation.


Funded by Marie-Curie International Outgoing Fellowship, Martin Llewellyn & ENGAGE project, NSERC, Canada, Nicolas Derome.


Pair-wise beta diversity measurements show destabilisation of Salmo salar skin mucus bacterial assemblages in response to infection with the sea louse L. salmonis.


Infected S. salar individual.

Links to Salmonid microbiota research:

In aquaculture, Atlantic Salmon face different challenges, including those associated with high intensity infection by copepod ectoparasites, such as Lepeophtheirus sea lice species.  Building on our baseline understanding of interactions between the host and its "healthy" microbiota, the next steps will include evaluating the role that salmon-associated microbiota play in mitigating – or exacerbating – the impact of these pathogens.

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