Virulence and pathogenicity of Francisella philomiragia subsp. noatunensis for Atlantic cod, Gadus morhua L., and laboratory mice

Establishment of Three Francisella Infections in Zebrafish Embryos at Different Temperatures

“…Inter-estingly, F. noatunensis subsp. noatunensis causes similar chronic infections in its natural host, the Atlantic cod (4,29,55), highlighting the strong potential of the zebrafish model. Another significant difference in the immune response of F. noatunensis subsp.…”

“…The mortality of Atlantic cod challenged with F. noatunensis subsp. noatunensis under experimental conditions is highly variable, ranging from 75% (12) to a few percent, even many months after challenge, when gross pathology is evident in the fish (4,29). Due to the slow progression of the disease, the inconsistent mortality of Atlantic cod, and the lack of alternate animal models (5), there is a need for establishment of models which allow faster development of the infection, giving more consistent results and hopefully providing insight into the Francisella sp.…”

“…novicida has low virulence in humans but is highly infectious to mice and has been widely used as a model for F. tularensis (2). F. noatunensis subspecies are essentially avirulent to mammals (4) but cause francisellosis in fish (5), resulting in large losses for the fish farming industry worldwide (6)(7)(8)(9)(10)(11). F. noatunensis consists of two subspecies, which appear to be adapted to different host temperatures: F. noatunensis subsp.…”

Fate of Francisella noatunensis, a pathogen of Atlantic cod Gadus morhua, in blue mussels Mytilus edulis

“…The mechanism by which Francisella noatunensis is shed into water by infected cod is not known, but infections are readily obtained in cohabitation challenges (Nylund et al 2006, Mikalsen et al 2009). Blue mussels are very common in the marine environment and feed on small particles in water, which also include bacteria e.g.…”

“…Francisellosis in cod is associated with reduced growth, mortalities, reduced quality, and elevated discard rates at slaughter, with corresponding economic losses (Nylund et al 2006). Knowledge of transmission mechanisms of F. noatunensis is scarce; however, horizontal transmission by cohabitation of cod kept at high temperatures has been shown in laboratory experiments (Nylund et al 2006, Mikalsen et al 2009). Field observations seem to support these findings, as the prevalence within infected stocks is often high (Colquhoun et al 2008, Ottem et al 2008).…”