704
minutes to several hours (‘bath’). It is essential that the compounds are soluble or, if
insoluble, are dispersed evenly in the water by means of surfactants or other dispersants (Austin et al. 1981 ). Also, seawater cations may well antagonise antimicrobial
compounds in seawater (Barnes et al. 1995 ). One major drawback, however, concerns the disposal of the spent compound. Ideally, it should not be released into the
aquatic environment, particularly if there are any abstraction points for potable
water supply systems in the vicinity. Neglect of this point could lead to legal
repercussions.
Flush treatments also involve the addition of drugs, albeit at high concentrations,
to the water in stock-holding areas. After addition, the drug is fl ushed through the
system by normal water fl ow. Flushing inevitably results in only a brief exposure to
the inhibitory compound; therefore, quick acting agents are absolutely necessary.
As before, the major problem is adequate disposal of the spent drug.
Injection of drug solutions is feasible for valuable stock, such as brood fi sh and
ornamental/pet fi sh. However, the technique is slow and will undoubtedly require
prior anaesthesia of the animals.
The topical application of antimicrobial compounds is worthy of consideration
for valuable and/or pet fi sh. In the case of ulcers, we recommend that the animal
should be gently removed from the water, and the antimicrobial compound (preferably as a powder) applied to the lesion, which is then sealed with a waterproof
covering, e.g. with dental paste. The lesions tend to heal quickly, with only limited
evidence of scarring.
Whatever the chosen method of application, drugs may be used for prevention,
i.e. prophylaxis, or treatment, i.e. chemotherapy, of fi sh diseases. Certainly, it is
comforting to note that there are treatments available for the majority of the bacterial fi sh pathogens. Providing that drugs are used prudently and correctly, they will
continue to offer relief from the rigours of disease for the foreseeable future.
Preventing the Movement and/or Slaughtering of Infected Stock
Some diseases, e.g. BKD, ERM and furunculosis, are suspected to be spread through
the movement of infected stock. Therefore, it is sensible to apply movement restrictions or even adopt a slaughter policy to diseased stock, as a means of disease control. This may prevent the spread of disease to both farmed and wild fi sh. Of course,
the issue of movement restrictions is highly emotive among fi sh farmers. However,
the procedure may be benefi cial to the industry when viewed as a whole. Certainly,
the concept of movement restrictions usually involves legislative machinery, of
which the Diseases of Fish Act (1983) in Great Britain is a prime example. To work
effectively, there is a requirement for both the effi cient monitoring of all stock at
risk to disease, and the dissemination of the information to all interested parties.
However, we believe that in any allegedly democratic society where such measures
are adopted, there should be adequate compensation to the fi sh farmer for loss of
revenue.
14 Control
minutes to several hours (‘bath’). It is essential that the compounds are soluble or, if
insoluble, are dispersed evenly in the water by means of surfactants or other dispersants (Austin et al. 1981 ). Also, seawater cations may well antagonise antimicrobial
compounds in seawater (Barnes et al. 1995 ). One major drawback, however, concerns the disposal of the spent compound. Ideally, it should not be released into the
aquatic environment, particularly if there are any abstraction points for potable
water supply systems in the vicinity. Neglect of this point could lead to legal
repercussions.
Flush treatments also involve the addition of drugs, albeit at high concentrations,
to the water in stock-holding areas. After addition, the drug is fl ushed through the
system by normal water fl ow. Flushing inevitably results in only a brief exposure to
the inhibitory compound; therefore, quick acting agents are absolutely necessary.
As before, the major problem is adequate disposal of the spent drug.
Injection of drug solutions is feasible for valuable stock, such as brood fi sh and
ornamental/pet fi sh. However, the technique is slow and will undoubtedly require
prior anaesthesia of the animals.
The topical application of antimicrobial compounds is worthy of consideration
for valuable and/or pet fi sh. In the case of ulcers, we recommend that the animal
should be gently removed from the water, and the antimicrobial compound (preferably as a powder) applied to the lesion, which is then sealed with a waterproof
covering, e.g. with dental paste. The lesions tend to heal quickly, with only limited
evidence of scarring.
Whatever the chosen method of application, drugs may be used for prevention,
i.e. prophylaxis, or treatment, i.e. chemotherapy, of fi sh diseases. Certainly, it is
comforting to note that there are treatments available for the majority of the bacterial fi sh pathogens. Providing that drugs are used prudently and correctly, they will
continue to offer relief from the rigours of disease for the foreseeable future.
Preventing the Movement and/or Slaughtering of Infected Stock
Some diseases, e.g. BKD, ERM and furunculosis, are suspected to be spread through
the movement of infected stock. Therefore, it is sensible to apply movement restrictions or even adopt a slaughter policy to diseased stock, as a means of disease control. This may prevent the spread of disease to both farmed and wild fi sh. Of course,
the issue of movement restrictions is highly emotive among fi sh farmers. However,
the procedure may be benefi cial to the industry when viewed as a whole. Certainly,
the concept of movement restrictions usually involves legislative machinery, of
which the Diseases of Fish Act (1983) in Great Britain is a prime example. To work
effectively, there is a requirement for both the effi cient monitoring of all stock at
risk to disease, and the dissemination of the information to all interested parties.
However, we believe that in any allegedly democratic society where such measures
are adopted, there should be adequate compensation to the fi sh farmer for loss of
revenue.
14 Control