699
It is diffi cult to identify any particular type of preparation which excels in terms of
protection. Unfortunately, even the best vaccines may not completely prevent the
occurrence of disease, sometimes necessitating the use of costly medicines to combat low levels of infection.
A potentially exciting and relevant development has involved the realization that
some molecules may have broad spectrum use as vaccine candidates by offering
protection against a range of pathogens. In this connection, recombinant GADPHs
offer cross protection with RPS values of >60 % (Li et al. 2011 ).
Methods of Vaccine Inactivation
Methods to inactivate whole cell preparations include the use of chemicals, namely
3 % (v/v) chloroform, 0.3–0.5 % (v/v) formalin and 0.5–3.0 % (v/v) phenol, heat
(e.g. 56 °C or 100 °C for 30 or 60 min), sonication, pressure (600 kgf/cm
2 for
5 min), electric current (100 mA at 12v DC for 5 s) lysis with sodium hydroxide at
pH 9.5 or with SDS (Austin 1984b ; Hossain and Kawai 2009 ). Commercially, most
interest has centred on use of formalin, which has given encouraging results with
numerous bacterial fi sh pathogens, including Aer. hydrophila, Edw. ictaluri, Ph.
damselae subsp. piscicida, Ps. anguilliseptica, V. anguillarum, V. ordalii and Ali.
salmonicida. However, it is unfortunate that only a few studies have been carried out
to compare different inactivated preparations.
Methods of Administering Vaccines to Fish
A number of methods of administering vaccines to fi sh have been tried with varying
degrees of success (see Austin 1984b ), and include:
• Injection, with or without the presence of adjuvant, such as FCA/FIA. This technique is slow, and will inevitably require prior anaesthesia of the animals.
Injection is only feasible for valuable fi sh, brood stock or pet fi sh. Fortunately,
mass injection techniques are available.
• Oral uptake, via food. This should be the method of choice insofar as fi sh could
be fed and vaccinated simultaneously. However, there may be problems with the
degradation of the vaccine in the gastro-intestinal tract, although this is being
overcome by new exciting oralising compounds.
• Immersion in a solution/suspension of the vaccine. This is quick (i.e. taking
30–120 s to perform) and easy, permitting large numbers of fi sh to be readily
vaccinated. However, there could be problems regarding disposal of the spent
vaccine. Thus, it is debatable whether or not disposal should take place in the fi sh
farm effl uent.
Farmed Fish
It is diffi cult to identify any particular type of preparation which excels in terms of
protection. Unfortunately, even the best vaccines may not completely prevent the
occurrence of disease, sometimes necessitating the use of costly medicines to combat low levels of infection.
A potentially exciting and relevant development has involved the realization that
some molecules may have broad spectrum use as vaccine candidates by offering
protection against a range of pathogens. In this connection, recombinant GADPHs
offer cross protection with RPS values of >60 % (Li et al. 2011 ).
Methods of Vaccine Inactivation
Methods to inactivate whole cell preparations include the use of chemicals, namely
3 % (v/v) chloroform, 0.3–0.5 % (v/v) formalin and 0.5–3.0 % (v/v) phenol, heat
(e.g. 56 °C or 100 °C for 30 or 60 min), sonication, pressure (600 kgf/cm
2 for
5 min), electric current (100 mA at 12v DC for 5 s) lysis with sodium hydroxide at
pH 9.5 or with SDS (Austin 1984b ; Hossain and Kawai 2009 ). Commercially, most
interest has centred on use of formalin, which has given encouraging results with
numerous bacterial fi sh pathogens, including Aer. hydrophila, Edw. ictaluri, Ph.
damselae subsp. piscicida, Ps. anguilliseptica, V. anguillarum, V. ordalii and Ali.
salmonicida. However, it is unfortunate that only a few studies have been carried out
to compare different inactivated preparations.
Methods of Administering Vaccines to Fish
A number of methods of administering vaccines to fi sh have been tried with varying
degrees of success (see Austin 1984b ), and include:
• Injection, with or without the presence of adjuvant, such as FCA/FIA. This technique is slow, and will inevitably require prior anaesthesia of the animals.
Injection is only feasible for valuable fi sh, brood stock or pet fi sh. Fortunately,
mass injection techniques are available.
• Oral uptake, via food. This should be the method of choice insofar as fi sh could
be fed and vaccinated simultaneously. However, there may be problems with the
degradation of the vaccine in the gastro-intestinal tract, although this is being
overcome by new exciting oralising compounds.
• Immersion in a solution/suspension of the vaccine. This is quick (i.e. taking
30–120 s to perform) and easy, permitting large numbers of fi sh to be readily
vaccinated. However, there could be problems regarding disposal of the spent
vaccine. Thus, it is debatable whether or not disposal should take place in the fi sh
farm effl uent.
Farmed Fish