541
Bypassing the potential deleterious effects of the stomach and upper regions of
the gastro-intestinal tract enables effective vaccination to proceed. This suggests
that micro-encapsulation techniques may be important for the development of successful oral vaccines. In this respect, the use of alginate microparticles has given
promising results with an orally administered V. anguillarum vaccine (Joosten et al.
1997 ). An interesting point is the implication that the posterior region of the gastrointestinal tract is involved with the correct functioning of oral vaccines. This region
has also been determined to be one of the initial sites of attachment of the pathogen.
Therefore, it may be inferred that the best protection stems from methods paralleling those of the natural infection cycle.
In contrast to oral methods, injection has proved to be excellent as a means of
vaccinating fi sh against vibriosis, with the development of high levels of immunity
(Antipa 1976 ; Antipa and Amend 1977 ; Sawyer and Strout 1977 ; Harrell 1978 ;
Evelyn and Ketcheson 1980 ). Evidence suggests that 24 h and up to 14 days (but not
21 days) after i.p. injection with formalin-killed whole cells, the bacteria migrate to
the spleen (particularly around small blood vessels when applied in FCA), heart,
kidney and peritoneum of Atlantic cod (Arnesen et al. 2002 ). Unfortunately, the
injection technique is slow, and seems feasible only for large and/or valuable fi sh.
Nevertheless, several types of preparations, including heat-killed and formalised
vaccines, have been evaluated by injection. In addition, passive immunisation (by
injection) has demonstrated the transfer of immunity between fi sh. In one comparison, it was clearly demonstrated that heat-killed preparations were more successful
than products treated with formalin, when administered by injection. Reference is
made to the work of Antipa ( 1976 ), who injected chinook salmon with vaccines and,
following challenge with the pathogen, reported cumulative mortalities of:
unvaccinated controls 85.4 %
formalised vaccine 37.8 %
heat-killed vaccine 22.3 %
Sonicated heat-killed vaccines, administered in adjuvant, also stimulate elevated
levels of antibody in the skin and mucus (Harrell et al. 1976 ; Evelyn 1984 ). At least
these studies indicate the presence of heat-stable antigen, which features signifi -
cantly in the establishment of protective immunity.
Anal intubation, but not i.p. injection, of African catfi sh (Clarias gariepinus)
with a whole cell vaccine of V. anguillarum O2 led to increased antibody levels after
14 days in the bile and skin mucus as detected by ELISA (Vervarcke et al. 2005 ).
Antibodies in a group vaccinated by oral intubation were lower, but still higher than
the i.p. vaccinated group (Vervarcke et al. 2005 ).
Immersion techniques are most suited for the vaccination of animals in the fi sh
farm environment. Formerly, considerable attention was focused on hyperosmotic
infi ltration, involving use of a strong salt solution prior to immersion in a vaccine
suspension (Croy and Amend 1977 ; Aoki and Kitao 1978 ; Nakajima and Chikahata
1979 ; Antipa et al. 1980 ; Giorgetti et al. 1981 ). However, it is now appreciated that
the technique is extremely stressful to fi sh (Busch et al. 1978 ), and the level of protection achieved is only comparable to the much simpler direct immersion method
Vibrio anguillarum
Bypassing the potential deleterious effects of the stomach and upper regions of
the gastro-intestinal tract enables effective vaccination to proceed. This suggests
that micro-encapsulation techniques may be important for the development of successful oral vaccines. In this respect, the use of alginate microparticles has given
promising results with an orally administered V. anguillarum vaccine (Joosten et al.
1997 ). An interesting point is the implication that the posterior region of the gastrointestinal tract is involved with the correct functioning of oral vaccines. This region
has also been determined to be one of the initial sites of attachment of the pathogen.
Therefore, it may be inferred that the best protection stems from methods paralleling those of the natural infection cycle.
In contrast to oral methods, injection has proved to be excellent as a means of
vaccinating fi sh against vibriosis, with the development of high levels of immunity
(Antipa 1976 ; Antipa and Amend 1977 ; Sawyer and Strout 1977 ; Harrell 1978 ;
Evelyn and Ketcheson 1980 ). Evidence suggests that 24 h and up to 14 days (but not
21 days) after i.p. injection with formalin-killed whole cells, the bacteria migrate to
the spleen (particularly around small blood vessels when applied in FCA), heart,
kidney and peritoneum of Atlantic cod (Arnesen et al. 2002 ). Unfortunately, the
injection technique is slow, and seems feasible only for large and/or valuable fi sh.
Nevertheless, several types of preparations, including heat-killed and formalised
vaccines, have been evaluated by injection. In addition, passive immunisation (by
injection) has demonstrated the transfer of immunity between fi sh. In one comparison, it was clearly demonstrated that heat-killed preparations were more successful
than products treated with formalin, when administered by injection. Reference is
made to the work of Antipa ( 1976 ), who injected chinook salmon with vaccines and,
following challenge with the pathogen, reported cumulative mortalities of:
unvaccinated controls 85.4 %
formalised vaccine 37.8 %
heat-killed vaccine 22.3 %
Sonicated heat-killed vaccines, administered in adjuvant, also stimulate elevated
levels of antibody in the skin and mucus (Harrell et al. 1976 ; Evelyn 1984 ). At least
these studies indicate the presence of heat-stable antigen, which features signifi -
cantly in the establishment of protective immunity.
Anal intubation, but not i.p. injection, of African catfi sh (Clarias gariepinus)
with a whole cell vaccine of V. anguillarum O2 led to increased antibody levels after
14 days in the bile and skin mucus as detected by ELISA (Vervarcke et al. 2005 ).
Antibodies in a group vaccinated by oral intubation were lower, but still higher than
the i.p. vaccinated group (Vervarcke et al. 2005 ).
Immersion techniques are most suited for the vaccination of animals in the fi sh
farm environment. Formerly, considerable attention was focused on hyperosmotic
infi ltration, involving use of a strong salt solution prior to immersion in a vaccine
suspension (Croy and Amend 1977 ; Aoki and Kitao 1978 ; Nakajima and Chikahata
1979 ; Antipa et al. 1980 ; Giorgetti et al. 1981 ). However, it is now appreciated that
the technique is extremely stressful to fi sh (Busch et al. 1978 ), and the level of protection achieved is only comparable to the much simpler direct immersion method
Vibrio anguillarum