Fate of Francisella noatunensis, a pathogen of Atlantic cod Gadus morhua, in blue mussels Mytilus edulis
Wangen, Ingvild H.; Karlsbakk, Egil; Einen, Ann Cathrine Bårdsgjære; Ottem, Karl; Nylund, Are; Mortensen, Stein H.
Journal article, Peer reviewed
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Date
2012-02-17Metadata
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http://dx.doi.org/10.3354/dao02427Abstract
Francisellosis, caused by the bacterium Francisella noatunensis, is one of the most
severe diseases affecting farmed cod, and has caused great economic loss for the cod farming
industry in Norway. We studied the fate of F. noatunensis in the marine environment, focusing on
the role of blue mussels. In experimental challenges, waterborne F. noatunensis was rapidly filtered
by the blue mussel and transported to the digestive diverticulae. The bacteria passed
through the entire digestive system. Intraperitoneal injection of cod with suspensions prepared
from faeces collected from challenged mussels resulted in the development of francisellosis in the
recipients, demonstrating that some bacteria were alive and infective when shed in mussel faeces.
Bacterial clearance from the mussels was relatively fast, and no evidence was found, suggesting
that the bacterium is capable of persisting or multiplying in the mussel tissues. A cohabitation
experiment with cod and mussels previously exposed to F. noatunensis did not lead to infection in
cod. A direct transmission from contaminated mussels to cod was thus not demonstrated; however,
faeces particles with infective bacteria may play a role in the transmission of the bacterium in
marine food chains.