293
study of Norqvist et al. ( 1989 ), it is necessary to question the need for incorporation
of Aer. salmonicida cells or their cellular components into furunculosis vaccines.
Injection techniques appear to be the most effi cacious, whereas the oral route is
least promising (Midtlyng et al. 1996 ). The use of adjuvants, especially mineral oil,
in injectable vaccines is clearly benefi cial (Midtlyng 1996 ) with 16S rRNA and LPS
being detected in the head kidney and spleen at 2 weeks (and in the head kidney at
12 weeks) after injection with a commercial oil adjuvanted, formalin-inactivated
vaccine (Grove et al. 2003 ). Indeed, Midtlyng ( 1996 ) determined from a fi eld study
in Norway that i.p. administration of furunculosis vaccine in a mineral oil adjuvant
gave the best protection in Atlantic salmon. Apart from the obvious benefi ts of FCA
(Olivier et al. 1985b ), the use of ß-1,3 glucan (Vita-Stim-Taito), lentinan and
formalin- killed cells of Ren. salmoninarum have enhanced the effectiveness of vaccines based on formalised Aer. salmonicida cells (Nikl et al. 1991 ). Possibly with
oral uptake, degradation of the vaccine in the gastro-intestinal tract may occur. In
this case, there may be potential for the use of micro-encapsulation techniques to
avoid such pitfalls. One interesting and relevant approach, which is reminiscent of
the probiotic saga, involved the i.p. administration of 10
7 cells/fi sh of a live auxotrophic aroA mutant of Aer. hydrophila that protected rainbow trout 30 days later
against furunculosis (RPS = >60 %) and stimulated the humoral and cellular immune
response (Vivas et al. 2004a).
Immersion techniques have generated much useful data. Rodgers ( 1990 ) reported
the benefi ts of using inactivated whole cells, toxoided ECP and LPS for the protection of juvenile salmonids. Moreover, the vaccinated animals grew better than the
controls. Work has indicated that the duration of the immersion vaccination process
does not affect the uptake of the vaccine, providing that the antigens are not in low
concentrations (Tatner 1987 ). Therefore, there appears to be some promise for the
widely used immersion vaccination technique with furunculosis vaccines.
Ultrasound has been used as a method to administer vaccines for the control of
goldfi sh ulcer disease. Thus, soluble A-protein was applied by immersion (100 μg
A-protein/ml for 10 min) after ultrasound (1 MHz frequency of ultrasound/1 min)
pre treatment, and led to promising results in goldfi sh against challenge (Navot et al.
2011 ). Furthermore, low frequency sonophoresis at 37 kHz has been used to increase
the uptake of antigens across rainbow trout skin by threefold, and without any signifi cant side effects (Cobo et al. 2014 ).
Traditionally, oral vaccines were considered to be the least successful insofar as
it was reasoned that the antigens became degraded during passage through the stomach and possibly there were issues regarding access to the antibody-producing sites.
Liposome-entrapped antigens of atypical Aer. salmonicida were fed to carp with the
result that there was a stimulation of the immune response, specifi cally the presence
of antibodies in bile, intestinal mucus and serum, and greater protection (less mortalities) and a reduction in ulceration compared to the controls (Irie et al. 2005 ).
Gradually, however, oral vaccines have attained favour, and commercial products
are now available.
Some of the diffi culties with ascertaining the effi cacy of vaccines have been
ascribed to methods of experimental challenge. Indeed, it is not unusual for vacAeromonas salmonicida
study of Norqvist et al. ( 1989 ), it is necessary to question the need for incorporation
of Aer. salmonicida cells or their cellular components into furunculosis vaccines.
Injection techniques appear to be the most effi cacious, whereas the oral route is
least promising (Midtlyng et al. 1996 ). The use of adjuvants, especially mineral oil,
in injectable vaccines is clearly benefi cial (Midtlyng 1996 ) with 16S rRNA and LPS
being detected in the head kidney and spleen at 2 weeks (and in the head kidney at
12 weeks) after injection with a commercial oil adjuvanted, formalin-inactivated
vaccine (Grove et al. 2003 ). Indeed, Midtlyng ( 1996 ) determined from a fi eld study
in Norway that i.p. administration of furunculosis vaccine in a mineral oil adjuvant
gave the best protection in Atlantic salmon. Apart from the obvious benefi ts of FCA
(Olivier et al. 1985b ), the use of ß-1,3 glucan (Vita-Stim-Taito), lentinan and
formalin- killed cells of Ren. salmoninarum have enhanced the effectiveness of vaccines based on formalised Aer. salmonicida cells (Nikl et al. 1991 ). Possibly with
oral uptake, degradation of the vaccine in the gastro-intestinal tract may occur. In
this case, there may be potential for the use of micro-encapsulation techniques to
avoid such pitfalls. One interesting and relevant approach, which is reminiscent of
the probiotic saga, involved the i.p. administration of 10
7 cells/fi sh of a live auxotrophic aroA mutant of Aer. hydrophila that protected rainbow trout 30 days later
against furunculosis (RPS = >60 %) and stimulated the humoral and cellular immune
response (Vivas et al. 2004a).
Immersion techniques have generated much useful data. Rodgers ( 1990 ) reported
the benefi ts of using inactivated whole cells, toxoided ECP and LPS for the protection of juvenile salmonids. Moreover, the vaccinated animals grew better than the
controls. Work has indicated that the duration of the immersion vaccination process
does not affect the uptake of the vaccine, providing that the antigens are not in low
concentrations (Tatner 1987 ). Therefore, there appears to be some promise for the
widely used immersion vaccination technique with furunculosis vaccines.
Ultrasound has been used as a method to administer vaccines for the control of
goldfi sh ulcer disease. Thus, soluble A-protein was applied by immersion (100 μg
A-protein/ml for 10 min) after ultrasound (1 MHz frequency of ultrasound/1 min)
pre treatment, and led to promising results in goldfi sh against challenge (Navot et al.
2011 ). Furthermore, low frequency sonophoresis at 37 kHz has been used to increase
the uptake of antigens across rainbow trout skin by threefold, and without any signifi cant side effects (Cobo et al. 2014 ).
Traditionally, oral vaccines were considered to be the least successful insofar as
it was reasoned that the antigens became degraded during passage through the stomach and possibly there were issues regarding access to the antibody-producing sites.
Liposome-entrapped antigens of atypical Aer. salmonicida were fed to carp with the
result that there was a stimulation of the immune response, specifi cally the presence
of antibodies in bile, intestinal mucus and serum, and greater protection (less mortalities) and a reduction in ulceration compared to the controls (Irie et al. 2005 ).
Gradually, however, oral vaccines have attained favour, and commercial products
are now available.
Some of the diffi culties with ascertaining the effi cacy of vaccines have been
ascribed to methods of experimental challenge. Indeed, it is not unusual for vacAeromonas salmonicida