700
• Bathing in a very dilute preparation of the vaccine for prolonged periods, i.e.
several hours. This is obviously very economic in the use of vaccine. It is feasible
that the technique could be carried out during routine periods of confi nement,
such as during transportation of the stock between sites. However, with immersion, careful thought needs to be given to the question of disposal.
• Spraying or showering the vaccine onto fi sh. This can be automated, such that
fi sh are vaccinated on conveyor belts during routine grading.
• Hyperosmotic infi ltration. This involves a brief immersion (30–60 s) in a strong
salt solution, i.e. 3–8 % (w/v) sodium chloride, followed by dipping for 30–60 s
into the vaccine. This method is very stressful to fi sh, and its use has been consequently reduced. However, En. faecalis, Lactococcus garvieae and Str. iniae,
which have been identifi ed from diseased farmed fi sh in Taiwan, have been the
subject of vaccine development involving formalin-inactivated whole cell preparations that were administered to Nile tilapia by hyperosmotic infi ltration leading
during the fi fth and sixth week after challenge to RPS values of 71.2–88.7 %.
Boosters did not improve protection (Young et al. 2012 ).
• Anal/oral intubation. In particular, anal intubation offers possibilities for bypassing the deleterious effects of the stomach and intestine. The technique is, however, cumbersome and requires further development.
• Ultrasonics/ultrasound (Zhou et al. 2002 ; Navot et al. 2011 ).
It is often diffi cult to determine which is the most effective method of vaccine application. The method of choice often refl ects the whims of the user as much as scientifi c reasoning. The available evidence suggests that oral administration fares least
well, although new approaches of micro-encapsulation offer promise. The use of
oral vaccination for booster doses, has been successful, such as with Aer. hydrophila, Aer. salmonicida, Fla. columnare, Ph. damselae subsp. piscicida, V. anguillarum, V. ordalii and Y. ruckeri vaccines; i.p. injection may better that oral uptake in
terms of the resultant humoral antibody titre and protection, although there is not
always a direct correlation between antibody-titre and protection. However, with
Edw. ictaluri, Edw. tarda, V. anguillarum and V. ordalii preparations, immersion has
been demonstrated as superior to injection. Similarly with the ‘vibrio’ vaccines, the
shower method exceeds injection in terms of resulting protection. There is a question mark about the difference between vaccines – particularly oral vaccines – and
immunostimulants/feed additives that also give health benefi ts including immunostimulation and protection against disease. The levels of protection between these
alternatives are often compatible, with the natural products being cheaper and easier
to adopt particularly in terms of regulatory machinery that is engrained in many
countries.
Traditionally, potency testing has been by infectivity experiments whereby vaccinated fi sh are challenged with a virulent culture of the pathogen, and mortalities
counted and used to calculate the RPS. The severity of the approach has focused
attention of regulatory authorities, and a stated aim is to move towards non-lethal
testing methods, notably the measurement of key immunological parameters, e.g.
antibody production, which may be measured by ELISA (Romstad et al. 2012 ).
14 Control
• Bathing in a very dilute preparation of the vaccine for prolonged periods, i.e.
several hours. This is obviously very economic in the use of vaccine. It is feasible
that the technique could be carried out during routine periods of confi nement,
such as during transportation of the stock between sites. However, with immersion, careful thought needs to be given to the question of disposal.
• Spraying or showering the vaccine onto fi sh. This can be automated, such that
fi sh are vaccinated on conveyor belts during routine grading.
• Hyperosmotic infi ltration. This involves a brief immersion (30–60 s) in a strong
salt solution, i.e. 3–8 % (w/v) sodium chloride, followed by dipping for 30–60 s
into the vaccine. This method is very stressful to fi sh, and its use has been consequently reduced. However, En. faecalis, Lactococcus garvieae and Str. iniae,
which have been identifi ed from diseased farmed fi sh in Taiwan, have been the
subject of vaccine development involving formalin-inactivated whole cell preparations that were administered to Nile tilapia by hyperosmotic infi ltration leading
during the fi fth and sixth week after challenge to RPS values of 71.2–88.7 %.
Boosters did not improve protection (Young et al. 2012 ).
• Anal/oral intubation. In particular, anal intubation offers possibilities for bypassing the deleterious effects of the stomach and intestine. The technique is, however, cumbersome and requires further development.
• Ultrasonics/ultrasound (Zhou et al. 2002 ; Navot et al. 2011 ).
It is often diffi cult to determine which is the most effective method of vaccine application. The method of choice often refl ects the whims of the user as much as scientifi c reasoning. The available evidence suggests that oral administration fares least
well, although new approaches of micro-encapsulation offer promise. The use of
oral vaccination for booster doses, has been successful, such as with Aer. hydrophila, Aer. salmonicida, Fla. columnare, Ph. damselae subsp. piscicida, V. anguillarum, V. ordalii and Y. ruckeri vaccines; i.p. injection may better that oral uptake in
terms of the resultant humoral antibody titre and protection, although there is not
always a direct correlation between antibody-titre and protection. However, with
Edw. ictaluri, Edw. tarda, V. anguillarum and V. ordalii preparations, immersion has
been demonstrated as superior to injection. Similarly with the ‘vibrio’ vaccines, the
shower method exceeds injection in terms of resulting protection. There is a question mark about the difference between vaccines – particularly oral vaccines – and
immunostimulants/feed additives that also give health benefi ts including immunostimulation and protection against disease. The levels of protection between these
alternatives are often compatible, with the natural products being cheaper and easier
to adopt particularly in terms of regulatory machinery that is engrained in many
countries.
Traditionally, potency testing has been by infectivity experiments whereby vaccinated fi sh are challenged with a virulent culture of the pathogen, and mortalities
counted and used to calculate the RPS. The severity of the approach has focused
attention of regulatory authorities, and a stated aim is to move towards non-lethal
testing methods, notably the measurement of key immunological parameters, e.g.
antibody production, which may be measured by ELISA (Romstad et al. 2012 ).
14 Control