531
V. anguillarum constitutes part of the normal microfl ora of the aquatic environment (e.g. West and Lee 1982 ; Muroga et al. 1986 ), particularly associated with
rotifers, which may become colonized (Tatani et al. 1985 ; Muroga and Yasunobu
1987 ; Mizuki et al. 2006 ; Prol-Garćia et al. 2010 ) and has been found in the digestive tract of cod larvae (Reid et al. 2009 ), with maximal and minimal numbers in
summer and winter, respectively (Larsen 1982 ). Experiments have suggested that
the pathogen survives in seawater (Prol-Garćia et al. 2010 ). Thus, Hoff ( 1989 )
reported survival for >50 months in a seawater microcosm. Additionally, experiments were conducted with V. anguillarum O2ß to determine a role for blue mussels
( Mytilus edulis ) to harbour and release the pathogen into the environment. Thus,
10
4 CFU of V. anguillarum /ml was introduced to mussels, which concentrated the
pathogen in the digestive gland tissues, with subsequent release in faeces
(10
7 CFU/g). These released bacteria were potentially harmful, and in challenge
experiments with cod by immersion resulted in substantial mortalities, i.e. 58–70 %.
However when the oysters were depurated, the pathogen could not be detected in
faeces within 72 h of depuration (Pietrak et al. 2012 ).
The organism may also constitute part of the normal microfl ora of marine fi sh
(Oppenheimer 1962 ; Mattheis 1964 ). Some elegant work, albeit with only one isolate, has addressed the precise changes to the organism, i.e. starvation-stress
responses, in the marine environment (Nelson et al. 1997 ) where Na
+ is essential for
starvation-survival (Fujiwara-Nagata and Eguchi 2004 ). When starved of carbon,
nitrogen and phosphorus, the number of colony forming units (note: this is a dubious measure of viability) dropped rapidly over an initial 5–7 day period, and then
gradually declined over 3–4 weeks. Some cells became small and spherical, corresponding to the notion of ultamicrobacteria (see Austin 1988 ), whereas others elongated to short spirals. Protein synthesis, as measured by incorporation of
[
35
S]-methionine declined during the fi rst 6 h of starvation, and increased to >70 %
of the rate in exponentially growing cells by 5 days into the starvation regime
(Nelson et al. 1997 ).
The precise origin of an isolate has importance for epizootiology. In this respect,
Olsen and Larsen ( 1990 ) detailed a seemingly useful method, namely restriction
fragment length polymorphism of the 65–70 kb plasmid. This method should have
value for epizootiological investigations.
The exact mode of infection is unclear, but undoubtedly involves colonisation of
(attachment to) the host, and thence penetration of the tissues. Ransom ( 1978 ) postulated that infection probably begins with colonisation of the posterior gastrointestinal tract and rectum. This conclusion resulted from the observation that V.
anguillarum was seen initially in these sites. Horne and Baxendale ( 1983 ) reported
adhesion of V. anguillarum to intestinal sections derived from rainbow trout. All
regions of the intestine were colonised (approximately 10
3 cells/cm
2 ), with maximum attachment occurring within 100 min. The skin appears to become colonised
within 12 h of immersion in a virulent culture (Kanno et al. 1990 ). Then, invasion
of the liver, spleen, muscle, gills and intestine follows (Muroga and De La Cruz
1987 ).
Vibrio anguillarum
V. anguillarum constitutes part of the normal microfl ora of the aquatic environment (e.g. West and Lee 1982 ; Muroga et al. 1986 ), particularly associated with
rotifers, which may become colonized (Tatani et al. 1985 ; Muroga and Yasunobu
1987 ; Mizuki et al. 2006 ; Prol-Garćia et al. 2010 ) and has been found in the digestive tract of cod larvae (Reid et al. 2009 ), with maximal and minimal numbers in
summer and winter, respectively (Larsen 1982 ). Experiments have suggested that
the pathogen survives in seawater (Prol-Garćia et al. 2010 ). Thus, Hoff ( 1989 )
reported survival for >50 months in a seawater microcosm. Additionally, experiments were conducted with V. anguillarum O2ß to determine a role for blue mussels
( Mytilus edulis ) to harbour and release the pathogen into the environment. Thus,
10
4 CFU of V. anguillarum /ml was introduced to mussels, which concentrated the
pathogen in the digestive gland tissues, with subsequent release in faeces
(10
7 CFU/g). These released bacteria were potentially harmful, and in challenge
experiments with cod by immersion resulted in substantial mortalities, i.e. 58–70 %.
However when the oysters were depurated, the pathogen could not be detected in
faeces within 72 h of depuration (Pietrak et al. 2012 ).
The organism may also constitute part of the normal microfl ora of marine fi sh
(Oppenheimer 1962 ; Mattheis 1964 ). Some elegant work, albeit with only one isolate, has addressed the precise changes to the organism, i.e. starvation-stress
responses, in the marine environment (Nelson et al. 1997 ) where Na
+ is essential for
starvation-survival (Fujiwara-Nagata and Eguchi 2004 ). When starved of carbon,
nitrogen and phosphorus, the number of colony forming units (note: this is a dubious measure of viability) dropped rapidly over an initial 5–7 day period, and then
gradually declined over 3–4 weeks. Some cells became small and spherical, corresponding to the notion of ultamicrobacteria (see Austin 1988 ), whereas others elongated to short spirals. Protein synthesis, as measured by incorporation of
[
35
S]-methionine declined during the fi rst 6 h of starvation, and increased to >70 %
of the rate in exponentially growing cells by 5 days into the starvation regime
(Nelson et al. 1997 ).
The precise origin of an isolate has importance for epizootiology. In this respect,
Olsen and Larsen ( 1990 ) detailed a seemingly useful method, namely restriction
fragment length polymorphism of the 65–70 kb plasmid. This method should have
value for epizootiological investigations.
The exact mode of infection is unclear, but undoubtedly involves colonisation of
(attachment to) the host, and thence penetration of the tissues. Ransom ( 1978 ) postulated that infection probably begins with colonisation of the posterior gastrointestinal tract and rectum. This conclusion resulted from the observation that V.
anguillarum was seen initially in these sites. Horne and Baxendale ( 1983 ) reported
adhesion of V. anguillarum to intestinal sections derived from rainbow trout. All
regions of the intestine were colonised (approximately 10
3 cells/cm
2 ), with maximum attachment occurring within 100 min. The skin appears to become colonised
within 12 h of immersion in a virulent culture (Kanno et al. 1990 ). Then, invasion
of the liver, spleen, muscle, gills and intestine follows (Muroga and De La Cruz
1987 ).
Vibrio anguillarum