The use of microwave radiation 700 W energy from a domestic microwave has been

The use of microwave radiation 700 w energy from a

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The use of microwave radiation (700 W energy from a domestic microwave) has been suggested for Pis. salmonis (Larenas et ai, 1996).
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7 Epizootiology: Gram-positive bacteria The reservoir of many Gram-positive bacterial fish pathogens is unknown. Whereas some groups, e.g. streptococci, occur in polluted waters, other organisms, e.g. Ren. salmoninarum, seem to be restricted to fish. How do such organisms spread between separate fish populations? ANAEROBES Clostridiaceae representative Clostridium botulinum CI. botulinum is widespread in soil, marine and freshwater sediments and in the gastro-intestinal tract of man and other animals, including fish (Bott et al., 1968; Cato et al., 1986). In one study of 530 trout in Danish earth ponds, CI. botulinum type E was discovered to occur in 5-100% of the fish in winter, and in 85-100% of the population in late summer (Huss et al, 1974a). It was supposed that the principal source of contamination with this organism was from minced trash fish used as feed, although soil and water could also be involved (Huss et al., 1974a). Moreover, it was considered Hkely that Clostridia become established in the mud and bottom-living invertebrates in trout ponds (Huss et al., 1974b). In Britain, it has been determined from an examination of 1,400 trout collected from 17 fish farms that the incidence of CI. botulinum in whole fish and viscera was 9.4% and 11.0%, respectively. Never- theless, CI. botulinum Hngers in the fish farm environment for considerable periods following outbreaks of disease. Thus, at the English trout farm which experienced botuHsm, the organism (possibly as endospores) was recovered for a year after the outbreak of disease. The numbers ranged from 1 to 800 organisms/g of sediment, compared with <l/g at an unaffected control site (Cann and Taylor, 1982). There are no data available to assess the level of contamination in wild fish stocks (Cann et al.
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238 Bacterial Fish Pathogens 1975). Similarly, there is no evidence to suggest that trout contaminated with CI. botulinum could comprise a human health hazard (Bach et al., 1971). Eubacteriaceae representative Eubacterium tarantellae So far, the organism has only been recovered from the brain of mullet and 10 other unnamed species of estuarine fish caught in Biscayne and Florida Bay. It has not been found outside this area. Moreover, the inability to grow in 2% (w/v) sodium chloride implies that the organism is likely to be restricted to estuarine environments (Udey et ai, 1977). These authors consider that isolates recovered from moribund fish, caught off the Texas coast and tentatively identified as Catenabacterium (Henley and Lewis, 1976), also belong in Eubacterium, as Eu. tarantellae. Therefore, the range would appear to be restricted to the warmer waters of the southern part of the U.S.A. It is uncertain whether or not the organism occurs in water, or indeed as part of the resident microflora offish, although Trust et al. (1979) isolated eubacteria from the intestinal tract of three fish species. Therefore, it is conceivable that Eu. tarantellae
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