Mycobacterium marinum ethyl alcohol 50 and 70 1

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Mycobacterium marinum Ethyl alcohol (50 and 70%), 1% benzyl-4-chlorophenol/phenylphenol and sodium chlorite (1:5:1 or 1:18:1 in the ratio of base: water: activator) were most effective at reducing or eliminating Myc. marinum within 1 min. Sodium hypochlorite (50,000 mg/1) was less effective, and needed 10 min contact time to reduce bacterial numbers. Ethyl alcohol (30%), 1:256 A^-alkyl-dimethyl-benzyl ammonium chloride and 1 % potassium peroxymonosulphate-NaCl were generally ineffective even after 1 h (Mainous and Smith, 2005). Renibacterium salmoninarum Disinfection of egg surfaces has also been utiHsed to control BKD. lodophors, at 25- 100 mg/1 for 5 min, have proved beneficial at reducing transmission of the disease (Amend and Pietsch, 1972; Ross and Smith, 1972; Bullock et al, 1978b), although they will not eliminate the pathogen from inside eggs (Evelyn et ai, 1984). The use of erythromycin phosphate, at 1-2 mg/1 for 30 min, has been advocated as an additive for water-hardening of eggs (Klontz, 1978). However, it is debatable whether or not it is wise to use antibiotics in this way. Another approach has been to disinfect the water in fish farms. In particular, a level of only 0.05 mg of free chlorine/1 was sufficient to inactivate cells of the pathogen in 18 sec (Pascho et ai, 1995). With such rapid inactivation, there must surely be a use for the technique in hatcheries. Staphylococcus aureus A bath of potassium permanganate (1 ml/1) for 5-10 min, together with treating the pond water with 250 mg/1 of lime and 1 mg/1 of potassium permanganate every fourth day, was considered effective at halting mortalities, except with advanced cases of the disease (Shah and Tyagi, 1986). 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 restric- tions or even adopt a slaughter poHcy to diseased stock, as a means of disease control. This may prevent the spread of disease to both farmed and wild fish. Of course, the issue of movement restrictions is highly emotive among fish farmers. However, the procedure may be beneficial to the industry when viewed as a whole. Evidence from Iceland has revealed that the culling of infected Atlantic salmon brood stock led to a reduction in the incidence of BKD (Gudmundsdottir et al, 2000). At the start of the
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Control 403 programme the incidence of infection was reported as ~35% of the brood stock on two ranch sites, but after a few years of adopting the programme of culHng the incidence fell to <2% (Gudmundsdottir et al, 2000). 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 efficient 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 fish farmer for loss of revenue.
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