701
Antimicrobial Compounds
There is a trend away from the use of antibiotic-like antimicrobial compounds in all
non-human applications with concerns about the possibility of tissue residues and
the development of bacterial resistance. It is astounding that so many compounds
(these have been reviewed by Snieszko 1978 ; Herwig 1979 ; Austin 1984a ) have
found use in aquaculture. The complete list reads like an inventory from any wellequipped pharmacy. Antibiotics, many of which are important in human medicine,
appear side by side with compounds used almost exclusively in fi sheries. In many
instances, the introduction of a compound into fi sheries use has followed closely
after the initial use in human medicine. Perhaps in retrospect, it is surprising that
there has not been any signifi cant furore from the medical profession about, what
could be perceived as misuse of pharmaceutical compounds.
The use of antimicrobial compounds in fi sheries essentially started with the work
of Gutsell ( 1946 ), who recognised the potential of sulphonamides for combating
furunculosis. Indeed, it may be argued that the effectiveness of sulphonamides led
to a temporary decline of interest in vaccine development. In fact, the eventual
emergence of antibiotic-resistant strains of fi sh pathogenic bacteria led to renewed
interest in vaccines. However during the years following the Second World War,
sulphonamides appeared to be the mystical saviour of fi sh farming. Important developments included the work of Rucker et al. ( 1951 ), who identifi ed sulphadiazine as
an effective chemotherapeutant for BKD. This claim was subsequently refuted by
Austin ( 1985 ). The next substantial improvement with sulphonamides resulted from
potentiation, i.e. the use of mixtures of trimethoprim and sulphonamide. These have
proved to be extremely useful for the treatment of furunculosis.
Following the introduction of sulphonamides, the range of antimicrobial compounds in aquaculture rapidly expanded to encompass chloramphenicol (Wold
1950 ), oxytetracycline (Snieszko and Griffi n 1951 ), kanamycin (Conroy 1961 ),
nifurprazine (Shiraki et al. 1970 ), oxolinic acid (Endo et al. 1973 ), sodium nifurstyrenate (Kashiwagi et al. 1977a , b ), fl umequine (Michel et al. 1980 ) and Baytril
(Bragg and Todd 1988 ). Unfortunately, detailed comparative studies of the various
antimicrobial compounds are rare; consequently it is often diffi cult to assess the
value of one drug (= any medicinal compound; Sykes 1976 ) over another.
Nevertheless, a pattern has emerged which points to the benefi ts of quinolines for
controlling diseases caused by a wide range of Gram-negative bacteria
Whatever the range of compounds available, their effectiveness is a function of
the method of administration to fi sh (and in the way in which it is carried out). We
have listed seven basic approaches to the administration of antimicrobial compounds to fi sh (Table 14.2 ). These are the oral route via medicated food and
bioencapsulation, bath, dip and fl ush treatments, injection and topical application.
With the oral method, drugs are mixed with food, and then fed to the fi sh. Usually,
the treatment regime leads to the administration of a unit weight of drug to a standard weight of fi sh per day for a pre-determined period. Examples of commonly
used antimicrobial compounds have been included in Table 14.3 . Fortunately, mediFarmed Fish
Antimicrobial Compounds
There is a trend away from the use of antibiotic-like antimicrobial compounds in all
non-human applications with concerns about the possibility of tissue residues and
the development of bacterial resistance. It is astounding that so many compounds
(these have been reviewed by Snieszko 1978 ; Herwig 1979 ; Austin 1984a ) have
found use in aquaculture. The complete list reads like an inventory from any wellequipped pharmacy. Antibiotics, many of which are important in human medicine,
appear side by side with compounds used almost exclusively in fi sheries. In many
instances, the introduction of a compound into fi sheries use has followed closely
after the initial use in human medicine. Perhaps in retrospect, it is surprising that
there has not been any signifi cant furore from the medical profession about, what
could be perceived as misuse of pharmaceutical compounds.
The use of antimicrobial compounds in fi sheries essentially started with the work
of Gutsell ( 1946 ), who recognised the potential of sulphonamides for combating
furunculosis. Indeed, it may be argued that the effectiveness of sulphonamides led
to a temporary decline of interest in vaccine development. In fact, the eventual
emergence of antibiotic-resistant strains of fi sh pathogenic bacteria led to renewed
interest in vaccines. However during the years following the Second World War,
sulphonamides appeared to be the mystical saviour of fi sh farming. Important developments included the work of Rucker et al. ( 1951 ), who identifi ed sulphadiazine as
an effective chemotherapeutant for BKD. This claim was subsequently refuted by
Austin ( 1985 ). The next substantial improvement with sulphonamides resulted from
potentiation, i.e. the use of mixtures of trimethoprim and sulphonamide. These have
proved to be extremely useful for the treatment of furunculosis.
Following the introduction of sulphonamides, the range of antimicrobial compounds in aquaculture rapidly expanded to encompass chloramphenicol (Wold
1950 ), oxytetracycline (Snieszko and Griffi n 1951 ), kanamycin (Conroy 1961 ),
nifurprazine (Shiraki et al. 1970 ), oxolinic acid (Endo et al. 1973 ), sodium nifurstyrenate (Kashiwagi et al. 1977a , b ), fl umequine (Michel et al. 1980 ) and Baytril
(Bragg and Todd 1988 ). Unfortunately, detailed comparative studies of the various
antimicrobial compounds are rare; consequently it is often diffi cult to assess the
value of one drug (= any medicinal compound; Sykes 1976 ) over another.
Nevertheless, a pattern has emerged which points to the benefi ts of quinolines for
controlling diseases caused by a wide range of Gram-negative bacteria
Whatever the range of compounds available, their effectiveness is a function of
the method of administration to fi sh (and in the way in which it is carried out). We
have listed seven basic approaches to the administration of antimicrobial compounds to fi sh (Table 14.2 ). These are the oral route via medicated food and
bioencapsulation, bath, dip and fl ush treatments, injection and topical application.
With the oral method, drugs are mixed with food, and then fed to the fi sh. Usually,
the treatment regime leads to the administration of a unit weight of drug to a standard weight of fi sh per day for a pre-determined period. Examples of commonly
used antimicrobial compounds have been included in Table 14.3 . Fortunately, mediFarmed Fish