127
Disease Control
Use of Antimicrobial Compounds As with mycobacteria, it has been argued that
infected fi sh should be destroyed so as to prevent any human health hazard. However,
some success may result with chemotherapy, in particular with sulphonamides, e.g.
sulphisoxazole at 2 mg/g of food (Van Duijn 1981 ). An improvement in the fi sh
becomes apparent within 10 days of the commencement of treatment, but it is
advisable to continue chemotherapy for 21 days. This method may be suitable for
the treatment of pet fi sh.
Nocardia asteroides
Characteristics of the Pathogen
There is limited information available about the characteristics of fi sh pathogenic
strains of Noc. asteroides.
Pathogenicity
Experimental infections have been established in Formosa snakehead (Chanos maculat) and largemouth bass (Micropterus salmoides) (Chen 1992 ). Thus, typical
granulomatous lesions and mortality followed in 14 days of i.p. or i.m. injection of
8 mg of suspensions of Noc. asteroides (Chen 1992 ).
Nocardia salmonicida (= Streptomyces salmonis = Streptoverticillum
salmonis)
Isolation
The organism may be isolated on glucose asparagine agar, glycerol asparagine agar
and yeast extract malt extract agar, Emerson agar. Bennett agar or nutrient agar,
Box 3.16: Nocardia asteroides
Most of the description appertains to morphological characters. For example,
it has been observed that cultures undergo a complete life cycle, including
germination from resting microcysts, simple and complex fi ssion, and branching. Thus, nocardias may appear in coccal to oval forms, and as long, slender,
multiseptate rods. All these stages have been seen in infected fi sh (Van Duijn
1981 ). From Valdez and Conroy ( 1963 ), it would appear that the organisms
reduce nitrates and degrade starch but not gelatin or urea. Neither H 2 S nor
indole is produced. The methyl red test and Voges-Proskauer reaction are
negative. Acid is produced from glucose, but not from any other carbohydrate
tested.
Nocardiaceae Representatives
Disease Control
Use of Antimicrobial Compounds As with mycobacteria, it has been argued that
infected fi sh should be destroyed so as to prevent any human health hazard. However,
some success may result with chemotherapy, in particular with sulphonamides, e.g.
sulphisoxazole at 2 mg/g of food (Van Duijn 1981 ). An improvement in the fi sh
becomes apparent within 10 days of the commencement of treatment, but it is
advisable to continue chemotherapy for 21 days. This method may be suitable for
the treatment of pet fi sh.
Nocardia asteroides
Characteristics of the Pathogen
There is limited information available about the characteristics of fi sh pathogenic
strains of Noc. asteroides.
Pathogenicity
Experimental infections have been established in Formosa snakehead (Chanos maculat) and largemouth bass (Micropterus salmoides) (Chen 1992 ). Thus, typical
granulomatous lesions and mortality followed in 14 days of i.p. or i.m. injection of
8 mg of suspensions of Noc. asteroides (Chen 1992 ).
Nocardia salmonicida (= Streptomyces salmonis = Streptoverticillum
salmonis)
Isolation
The organism may be isolated on glucose asparagine agar, glycerol asparagine agar
and yeast extract malt extract agar, Emerson agar. Bennett agar or nutrient agar,
Box 3.16: Nocardia asteroides
Most of the description appertains to morphological characters. For example,
it has been observed that cultures undergo a complete life cycle, including
germination from resting microcysts, simple and complex fi ssion, and branching. Thus, nocardias may appear in coccal to oval forms, and as long, slender,
multiseptate rods. All these stages have been seen in infected fi sh (Van Duijn
1981 ). From Valdez and Conroy ( 1963 ), it would appear that the organisms
reduce nitrates and degrade starch but not gelatin or urea. Neither H 2 S nor
indole is produced. The methyl red test and Voges-Proskauer reaction are
negative. Acid is produced from glucose, but not from any other carbohydrate
tested.
Nocardiaceae Representatives