294
cines to appear to work in laboratory conditions but to fail dismally in fi eld trials.
Under such circumstances, it is questionable whether or not meaningful challenge
techniques have been used. For example, the precise dosage of cells to be employed
remains undetermined. Apparently, there is substantial variation in virulence among
strains. In addition, the most effective means of administering the challenges
remains to be elucidated. In this respect, Michel ( 1980 ) and Cipriano ( 1982b ) suggested standardized methods of challenge. However, the effectiveness of these techniques awaits clarifi cation.
It is readily admitted that much effort has been expended on the development of
furunculosis vaccines. Yet, after 40 years the quest continues. Most studies, to date,
have measured effectiveness in terms of the humoral antibody response (e.g. Michel
et al. 1990 ). Unfortunately, there is now some doubt as to whether the presence of
humoral agglutinins actually correlates with protection. Maybe, it would be preferable to emphasise other aspects of fi sh immunology, such as cell-mediated immunity, a notion, which has been suggested by McCarthy and Roberts ( 1980 ).
Ford et al. ( 1998 ) treated sea run salmon broodstock with oxolinic acid and vaccinated with a formalised whole cell vaccine in an attempt to reduce the impact of
furunculosis. Encouraging results were obtained insofar as of 2552 fi sh captured
from the rivers Connecticut and Merrimack and treated in 1986–1992, only 362
died of which 65 (18 %) were diagnosed with furunculosis. In comparison, 206 fi sh
served as untreated controls, with just over half, i.e. 109, dying, of which 63 (=58 %)
had furunculosis.
There is ongoing concern about the value of furunculosis vaccines developed for
use in salmonids, and containing antigens of Aer. salmonicida subsp. salmonicida,
for application in other groups of fi sh, which may be affected by atypical isolates of
the pathogen. For example, a commercial polyvalent product for salmon failed to
protect turbot from experimental challenge with Aer. salmonicida subsp.
achromogenes (Björnsdóttir et al. 2005 ). However, Santos et al. ( 2005 ) appear to
have experienced better success with turbot, although the specifi c pathogen was not
equated with subsp. achromogenes . Nevertheless, the commercial vaccine, Furovac
5, and an autogenous vaccine resulted in RPS of 72–99 % when challenged 120
days after administration intraperitoneally. Even after 6-months, there was still reasonable protection (RPS = 50–52 %). In contrast, vaccination by immersion did not
lead to signifi cant protection. Interestingly, an oral booster dose did not improve
protection (Santos et al. 2005 ).
Immunostimulants/Dietary Supplements Kitao and Yoshida ( 1986 ) found that
synthetic peptides could enhance resistance of rainbow trout to Aer. salmonicida.
Administration of Baypamum to rainbow trout led to a reduction in symptoms and
mortalities attributed to furunculosis (Ortega et al. 1996 ). Dimerised lysozyme,
which is regarded as less toxic than the monomer, was injected into rainbow trout at
a dose of 10 or 100 μg/kg, and stimulated cellular and humoral mechanisms giving
protection against furunculosis (Siwicki et al. 1998 ). One and three injections of
lysozyme led to 45 % and 25 % mortalities following challenge with Aer. salmonicida. This compares to 85 % mortality among the untreated controls (Siwicki et al.
5 Aeromonadaceae Representative (Aeromonas salmonicida)
cines to appear to work in laboratory conditions but to fail dismally in fi eld trials.
Under such circumstances, it is questionable whether or not meaningful challenge
techniques have been used. For example, the precise dosage of cells to be employed
remains undetermined. Apparently, there is substantial variation in virulence among
strains. In addition, the most effective means of administering the challenges
remains to be elucidated. In this respect, Michel ( 1980 ) and Cipriano ( 1982b ) suggested standardized methods of challenge. However, the effectiveness of these techniques awaits clarifi cation.
It is readily admitted that much effort has been expended on the development of
furunculosis vaccines. Yet, after 40 years the quest continues. Most studies, to date,
have measured effectiveness in terms of the humoral antibody response (e.g. Michel
et al. 1990 ). Unfortunately, there is now some doubt as to whether the presence of
humoral agglutinins actually correlates with protection. Maybe, it would be preferable to emphasise other aspects of fi sh immunology, such as cell-mediated immunity, a notion, which has been suggested by McCarthy and Roberts ( 1980 ).
Ford et al. ( 1998 ) treated sea run salmon broodstock with oxolinic acid and vaccinated with a formalised whole cell vaccine in an attempt to reduce the impact of
furunculosis. Encouraging results were obtained insofar as of 2552 fi sh captured
from the rivers Connecticut and Merrimack and treated in 1986–1992, only 362
died of which 65 (18 %) were diagnosed with furunculosis. In comparison, 206 fi sh
served as untreated controls, with just over half, i.e. 109, dying, of which 63 (=58 %)
had furunculosis.
There is ongoing concern about the value of furunculosis vaccines developed for
use in salmonids, and containing antigens of Aer. salmonicida subsp. salmonicida,
for application in other groups of fi sh, which may be affected by atypical isolates of
the pathogen. For example, a commercial polyvalent product for salmon failed to
protect turbot from experimental challenge with Aer. salmonicida subsp.
achromogenes (Björnsdóttir et al. 2005 ). However, Santos et al. ( 2005 ) appear to
have experienced better success with turbot, although the specifi c pathogen was not
equated with subsp. achromogenes . Nevertheless, the commercial vaccine, Furovac
5, and an autogenous vaccine resulted in RPS of 72–99 % when challenged 120
days after administration intraperitoneally. Even after 6-months, there was still reasonable protection (RPS = 50–52 %). In contrast, vaccination by immersion did not
lead to signifi cant protection. Interestingly, an oral booster dose did not improve
protection (Santos et al. 2005 ).
Immunostimulants/Dietary Supplements Kitao and Yoshida ( 1986 ) found that
synthetic peptides could enhance resistance of rainbow trout to Aer. salmonicida.
Administration of Baypamum to rainbow trout led to a reduction in symptoms and
mortalities attributed to furunculosis (Ortega et al. 1996 ). Dimerised lysozyme,
which is regarded as less toxic than the monomer, was injected into rainbow trout at
a dose of 10 or 100 μg/kg, and stimulated cellular and humoral mechanisms giving
protection against furunculosis (Siwicki et al. 1998 ). One and three injections of
lysozyme led to 45 % and 25 % mortalities following challenge with Aer. salmonicida. This compares to 85 % mortality among the untreated controls (Siwicki et al.
5 Aeromonadaceae Representative (Aeromonas salmonicida)