Occurrence of Flavobacterium psychrophilum in fish-farming environments

Abstract

Occurrence of Flavobacterium psychrophilum in fish farms and fish-farming environments was studied using agar plate cultivation,the immunoflourescence antibody technique (IFAT) and nested PCR. Characteristics of 64 F. psychrophilum isolates from rainbow trout Oncorhynchus mykiss, fish farm rearing water, ovarian fluid and wild fish were serotyped, ribotyped and compared biochemically. Virulence of F. psychrophilum isolates from different sources was compared by injection into rainbow trout. Additionally, the number of F. psychrophilum cells shed by naturally infected rainbow trout was determined. F. psychrophilum was detected and isolated from skin mucus, skin lesions and internal organs of diseased rainbow trout and from fish without clinical disease. The pathogen was also present in wild perch Perca fluviatilis, roach Rutilus rutilus, and ovarian fluids of farmed rainbow trout brood fish. Isolates were biochemically homogenous, excluding the capability to degrade elastin. Five different agglutination patterns with different antisera against F. psychrophilum were found among the isolates studied. Although several different ribopatterns were found (ClaI: 12 ribopatterns and HaeIII: 9 ribopatterns), ribotype A was the most dominant. Farmed rainbow trout brood fish carried a broad-spectrum of serologically and genetically different F. psychrophilum in ovarian fluids. Virulence of the tested isolates in rainbow trout varied and naturally infected rainbow trout shed 10 4 to 10 8 cells fish -1 h -1 of F. psychrophilum into the surrounding water.KEY WORDS: Flavobacterium psychrophilum · Rainbow trout · Rearing water · Ovarian fluid · Perch · Roach · Shedding rate · Serotyping · Ribotyping Resale or republication not permitted without written consent of the publisherDis Aquat Org 52: 109-118, 2002, Cepeda & Santos 2000, Izumi & Wakabayashi 2000, Madetoja & Wiklund 2002. Flavobacterium psychrophilum has been isolated mainly from diseased and covertly infected salmonids (Holt et al. 1993. Infected living and dead fish are potential sources of F. psychrophilum infection that could possibly spread this pathogen in surrounding water (Madetoja et al. 2000). The shedding rate of F. psychrophilum by artificially infected fish has been evaluated in a previous study (Madetoja et al. 2000), but the shedding rate by naturally infected fish has not.In addition to the detection and isolation of Flavobacterium psychrophilum from cultured salmonids and ayu, the pathogen has also been detected in fish farm rearing water (Rangdale 1995, Madetoja & Wiklund 2002, on algae (Amita et al. 2000), in reproductive products of salmonids (Holt 1987, Rangdale et al. 1996, Brown et al. 1997, Ekman et al. 1999, in diseased cultured carp Cyprinus carpio, tench Tinca tinca, crucian carp Carassius carassius and in diseased wild eel Anguilla anguilla (Lehmann et al. 1991), in wild pale chub Zacco platypus (Iida & Mizokami 1996) and in a newt (Brown et al. 1997). Thus, several sources may act as a potential reservoir of infection.Typing techniq...

Detection of Flavobacterium psychrophilum in Chum Salmon Oncorhynchus keta and Virulence of Isolated Strains to Salmonid Fishes

“…Previous studies showed that F. psychrophilum is transmitted both horizontally (Madsen and Dalsgaard, 1999;Garcia et al, 2000;Madetoja et al, 2000) and vertically (Brown et al, 1997;Kumagai et al, 2000;Cipriano, 2005). Furthermore, F. psychrophilum has been detected in ovarian fluid, skin mucous, and internal organs of salmonid fish with no disease signs (Holt et al, 1993;Madetoja et al, 2002;Madsen et al, 2005). The presence of F. psychrophilum with high frequency would be potential source of infection to salmonid fish including chum salmon adult female and fry because the pathogen is virulent to salmonid fish juveniles as suggested in this study.…”

An Overview of the Immunological Defenses in Fish Skin

“…Simply by being slightly more hydrated, the fluid could have a markedly lower viscoelasticity and be readily penetrable by motile bacteria [82]. In fact, in challenge experiments with bacteria, removal of mucus/epidermal cells increased the cumulative mortality in salmonids compared to undamaged fishes [266,267].…”

Phase variation in Flavobacterium psychrophilum: characterization of two distinct colony phenotypes

“…The bacterial cells were biochemically characterized using tests suitable for Flavobacterium psychrophilum, including hydrolysis of starch (Pacha 1968), casein (Bernardet 1989), gelatin, esculin (Madetoja et al 2001) and elastin, production of catalase (Madetoja et al 2002), absorption of Congo red (Ishiguro et al 1985), presence of flexirubin-type pigments ) and cytochrome oxidase activity using the BBL TM Oxidase Reagent Droppers (BD). The enzymatic activity of the bacterial cells was also tested using a semi-quantitative micromethod, API ZYM (bioMérieux), in which the strips were incubated for 17 to 19 h at 15°C.…”