could comprise part of the anaerobic microflora of the digestive tract although

Could comprise part of the anaerobic microflora of

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could comprise part of the anaerobic microflora of the digestive tract, although it will be necessary for further study to clarify this point. GRAM-POSITIVE BACTERIA—THE "LACTIC ACID" BACTERIA Carnobacteriaceae representative Carnobacterium piscicola (and the lactobacilli) So far, it would appear that the disease is confined to Europe and North America. However, it is unclear whether fish are the natural hosts for Car. piscicola and other lactobacilli, or if they comprise part of the natural aquatic microflora. Streptococcaceae representatives Streptococcicosis (= streptococcosis) was initially described among populations of rainbow trout farmed in Japan (Hoshina et al, 1958). Since then, the disease has increased in importance, with outbreaks occurring in yellowtails (Kusuda et al., 1976a; Kitao et al., 1979), coho salmon (Atsuta et al., 1990), Jacopever (Sebastes schlegeli) (Sakai et al., 1986), Japanese eels (Kusuda et al., 1978b), ayu and tilapia (Kitao et al, 1981). The disease, also known as "pop-eye", has assumed importance in rainbow trout farms in Australia, Israel, Italy and South Africa (Barham et al, 1979; Boomker et al, 1979; Carson and Munday, 1990; Ceschia et al, 1992; B. Austin, unpublished data) and in Atlantic croaker (Micropogon undulatus), blue fish (Pomatomus saltatrix), channel catfish, golden shiner (Notemigonous chrysoleuca), hardhead (sea) catfish (Ariusfelis), menhaden (Brevoortiapatronus), pinfish (Lagodon rhomboides), sea trout (Cynoscion regalis), silver trout (Cynoscion nothus), spot (Leiostomus xanthurus), stingray (Dasyatis sp.), striped bass (Morone saxatilis) and
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Epizootiology: Gram-positive bacteria 239 striped mullet (Mugil cephalus) in the U.S.A. (Robinson and Meyer, 1966; Plumb et ai, 1974; Cook and Lofton, 1975; Baya et ai, 1990c). The disease may also have occurred sporadically in Great Britain and Norway. There is good evidence that streptococcicosis is problematical in both farmed and wild fish stocks. There is evidence that the pathogens abound throughout the year in the aquatic environment, occurring in water, mud and in the vicinity of fish pens (Kitao et ai, 1979). Some seasonality has been recorded, with higher numbers present in seawater during the summer. In contrast, greatest numbers were isolated in mud during autumn and winter (Kitao et al, 1979). This is interesting information, but unfortu- nately the authors do not comment further about the reasons for the presence of streptococci in the aquatic environment. Conceivably, the organisms may have been released from infected fish and were being merely retained in the water and under- lying sediment. Alternatively, with the inconclusive taxonomic status of the fish- pathogenic streptococci, it is difficult to conclude that any environmental isolates correspond precisely to the description of the pathogens. Therefore, any environ- mental isolates could be merely indicators of an unsanitary condition and not neces- sarily imply the presence offish-pathogenic strains. However, this evades the question about the precise source of infection. Minami (1979) determined that streptococci,
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