283
nosuppression following the administration of some vaccines (Inglis et al. 1996 ).
One solution to this problem has been the use of antibiotics, namely amoxicillin
dosed at 0.1 ml containing 150 mg/fi sh, which are administered by injection with
the vaccine (Inglis et al. 1996 ). However compared to the problems with salmon,
rainbow trout have been successfully protected using a 5 min bath in a formalininactivated whole cell preparation with or without a booster (>93 % survival compared to 70 % survival of the controls 10-weeks later) (Villumsen and Raida 2013 ).
The precise composition of the vaccine is of critical importance. To date, scientists have evaluated inactivated whole cells (including those based on IROMP, inactivated L-forms, soluble extracts, attenuated live cells (such as those lacking A-layer
and O-antigen; Thornton et al. 1994 ), inactivated cells supplemented with toxoids
and/or purifi ed sub-cellular components, immune serum (for passive immunisation)
and polyvalent preparations, usually including inactivated whole cells of Aer. salmonicida and Vibrio spp. (e.g. Hoel et al. 1997 ). Most of the early formulations
yielded poor or equivocal results (Table 5.3 ). The notable exceptions are passive
immunisation and the use of attenuated live vaccines (Cipriano and Starliper 1982 ;
Ellis et al. 1988a , b ; Vaughan et al. 1993 ). The latter was particularly effective in
Atlantic salmon, in which experimental use resulted in 12.5 % mortalities in the vaccinated group compared to 87.5 % mortality among control fi sh, after challenge
with a virulent culture of Aer. salmonicida. A live aromatic-dependent Aer. salmonicida vaccine, aroA was administered intraperitoneally at 2 × 10
6 to 2 × 10
9 live bacteria/fi sh, resulting in a 253-fold increase in LD 50 (Vaughan et al. 1993 ). This live
vaccine stimulated T-cells rather than B-cell responses in rainbow trout (Marsden
et al. 1996a ). But how long did this live vaccine remain in fi sh tissues? The evidence
revealed that following i.p. injection, the live vaccine became widely distributed
throughout fi sh (in this case rainbow trout) tissues, with clearance taking 7–9 d at
16 °C. Lower temperatures led to more prolonged retention of the bacterial cells
within the vaccinated fi sh (Marsden et al. 1996b ).
The novel approaches of using IROMP and inactivated L-forms have met with
success (Durbin et al. 1999 ; McIntosh and Austin 1993 ). Using formalin-inactivated
cells of Aer. salmonicida subsp. salmonicida grown in iron-depleted conditions
administered to rainbow trout intraperitoneally followed by an oral boost, antibodies were produced against OMP (maximum titre = 1:2560 at day 105) and IROMPs
(maximum titre = 1:12,800 at day 105) and conferred protection (RPS = >80 %;
Durbin et al. 1999 ). A complex formulation of atypical Aer. salmonicida cells (with,
but not without. A-layer) grown in iron-deplete and iron-supplementation plus cells
of Aer. bestiarum grown in TSB successfully protected goldfi sh against ulcer disease (RPS = >90 %) when administered by immersion (~5 × 10
7 cells/ml for 60 s)
followed by oral boosting over 7 days after 28 days (5 × 10
7 cells/g of feed)
(Robertson et al. 2005 ). Avirulent cells, with altered A-layer, have also been proposed as candidates for live vaccines (Thornton et al. 1991 ). However, a complication to the various developmental studies comes from the fascinating work of
Norqvist et al. ( 1989 ), who used live attenuated cells of a different bacterial taxon,
namely V. salmonicida, and reported their effectiveness at controlling infections by
Aer. salmonicida.
Aeromonas salmonicida
nosuppression following the administration of some vaccines (Inglis et al. 1996 ).
One solution to this problem has been the use of antibiotics, namely amoxicillin
dosed at 0.1 ml containing 150 mg/fi sh, which are administered by injection with
the vaccine (Inglis et al. 1996 ). However compared to the problems with salmon,
rainbow trout have been successfully protected using a 5 min bath in a formalininactivated whole cell preparation with or without a booster (>93 % survival compared to 70 % survival of the controls 10-weeks later) (Villumsen and Raida 2013 ).
The precise composition of the vaccine is of critical importance. To date, scientists have evaluated inactivated whole cells (including those based on IROMP, inactivated L-forms, soluble extracts, attenuated live cells (such as those lacking A-layer
and O-antigen; Thornton et al. 1994 ), inactivated cells supplemented with toxoids
and/or purifi ed sub-cellular components, immune serum (for passive immunisation)
and polyvalent preparations, usually including inactivated whole cells of Aer. salmonicida and Vibrio spp. (e.g. Hoel et al. 1997 ). Most of the early formulations
yielded poor or equivocal results (Table 5.3 ). The notable exceptions are passive
immunisation and the use of attenuated live vaccines (Cipriano and Starliper 1982 ;
Ellis et al. 1988a , b ; Vaughan et al. 1993 ). The latter was particularly effective in
Atlantic salmon, in which experimental use resulted in 12.5 % mortalities in the vaccinated group compared to 87.5 % mortality among control fi sh, after challenge
with a virulent culture of Aer. salmonicida. A live aromatic-dependent Aer. salmonicida vaccine, aroA was administered intraperitoneally at 2 × 10
6 to 2 × 10
9 live bacteria/fi sh, resulting in a 253-fold increase in LD 50 (Vaughan et al. 1993 ). This live
vaccine stimulated T-cells rather than B-cell responses in rainbow trout (Marsden
et al. 1996a ). But how long did this live vaccine remain in fi sh tissues? The evidence
revealed that following i.p. injection, the live vaccine became widely distributed
throughout fi sh (in this case rainbow trout) tissues, with clearance taking 7–9 d at
16 °C. Lower temperatures led to more prolonged retention of the bacterial cells
within the vaccinated fi sh (Marsden et al. 1996b ).
The novel approaches of using IROMP and inactivated L-forms have met with
success (Durbin et al. 1999 ; McIntosh and Austin 1993 ). Using formalin-inactivated
cells of Aer. salmonicida subsp. salmonicida grown in iron-depleted conditions
administered to rainbow trout intraperitoneally followed by an oral boost, antibodies were produced against OMP (maximum titre = 1:2560 at day 105) and IROMPs
(maximum titre = 1:12,800 at day 105) and conferred protection (RPS = >80 %;
Durbin et al. 1999 ). A complex formulation of atypical Aer. salmonicida cells (with,
but not without. A-layer) grown in iron-deplete and iron-supplementation plus cells
of Aer. bestiarum grown in TSB successfully protected goldfi sh against ulcer disease (RPS = >90 %) when administered by immersion (~5 × 10
7 cells/ml for 60 s)
followed by oral boosting over 7 days after 28 days (5 × 10
7 cells/g of feed)
(Robertson et al. 2005 ). Avirulent cells, with altered A-layer, have also been proposed as candidates for live vaccines (Thornton et al. 1991 ). However, a complication to the various developmental studies comes from the fascinating work of
Norqvist et al. ( 1989 ), who used live attenuated cells of a different bacterial taxon,
namely V. salmonicida, and reported their effectiveness at controlling infections by
Aer. salmonicida.
Aeromonas salmonicida