MISCELLANEOUS PATHOGENS Unknown Gram negative rod According to Palmer et al

Miscellaneous pathogens unknown gram negative rod

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MISCELLANEOUS PATHOGENS Unknown Gram-negative rod According to Palmer et al. (1994), the pathogen was susceptible to amoxycilHn and penicillin G, but resistant to cotrimoxazole and oxytetracycline.
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Control 401 DISINFECTION/WATER TREATMENTS Apart from the use of antibiotics and related compounds, the appHcation of other chemicals to water as disinfectants is effective for disease control Such chemicals include benzalkonium chloride, chloramine B and T, chlorine, formahn, iodophors, malachite green and methylene blue. For example, Sato et al. (1982) used chlorine to disinfect water, and thus control infection by Cit. freundii. Another approach is to alter (increase or decrease, according to the season) the temperature of water within fish-holding facilities. We have noticed that this approach appears to be effective at reducing the incidence of diseases such as columnaris. Specifically: Aeromonas salmonicida Adequate husbandry practices—such as maintenance of good water quality, disin- fection offish farm equipment and utensils—especially when disease outbreaks occur, and routine disinfection policies for eggs upon arrival at receiving sites (Herman, 1972; McCarthy and Roberts, 1980). Citrobacter freundii Outbreaks of the disease abated following adoption of water disinfection (with chlorine) practices (Sato et al, 1982). Clostridium botulinum As there is no effective chemotherapy for botuHsm in fish, disinfection of the ponds has been advocated. Success has resulted from moving the stock to clean areas, draining the contaminated ponds, and removing surface mud and detritus before disinfecting with slaked lime at 1.6kg/m^. The disinfectant should be worked well into the layers at the bottom of the ponds, left for a period of not less than 7 days, and the pond then returned to use (Huss et al, 1974; Cann and Taylor, 1982). To remove Clostridia from the gastro-intestinal tract of trout, it has been recommended that the fish should be starved for 5 days (Wenzel et al., 1971). However, Huss et al. (1974) showed that, whereas starvation does indeed reduce contamination with C. botuli- num, the overall rate of success depends on other factors, including the nature of the water supply. It should be emphasised that Clostridia may be normal inhabitants of the fish intestine. Flavobacterium columnar e Diquat was effective as a bath treatment for channel catfish, effectively stopping mortalities caused by the pathogen. Also, there was some reduction in mortahties following bathing in chloramine T and potassium permanganate, but not so with copper sulphate and hydrogen peroxide (Thomas-Jinu and Goodwin, 2004). Experi- ments with rainbow trout fingerlings have demonstrated a potential for the use of
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402 Bacterial Fish Pathogens sodium chloride baths in reducing mortahties caused by columnaris following water- borne challenge (Suomalainen et ai, 2005).
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