410
Flavobacterium columnare (=Flexibacter/Cytophaga
columnaris)
Characteristics of the Disease
Columnaris has been recognised to have worldwide distribution in a wide range of
freshwater fi sh, including Arctic charr, bass, black bullheads, carp, channel catfi sh,
chub, eel, goldfi sh, killifi sh, loach, perch, rainbow trout, roach, Atlantic salmon,
chinook salmon, sheatfi sh, squawfi sh, tilapia, white crappie, whitefi sh and whitesuckers (Nigrelli 1943 ; Nigrelli and Hutner 1945 ; Wakabayashi and Egusa 1966 ;
Ajmal and Hobbs 1967 ; Fijan 1969 ; Bowser 1973 ; Wobeser and Atton 1973 ; Chun
1975 ; Bootsma and Clerx 1976 ; Ferguson 1977 ; Farkas and Oláh 1980 ; Kuo et al.
1981 ; Morrison et al. 1981 ; Chen et al. 1982 ; Koski et al. 1993 ; Welker et al. 2005 ).
The disease was considered to be suffi ciently serious to warrant inclusion in the list
of notifi able fi sh diseases, as defi ned by the (British) Diseases of Fish Act, 1937.
However, columnaris was omitted from the 1983 Act.
Infection with Fla. columnare may result in several discrete disease conditions.
In young fi sh, there is often negligible pathology before death ensues. The gill is
usually the major site of damage. Typically, congestion (blockage) of the blood vessels supplying the gills occurs, with dissociation of the surface epithelium of the
lamellae from the capillary bed. There may be scattered areas of haemorrhaging
(Pacha and Ordal 1967 ). In adult fi sh, the lesions may occur on the gills, skin and/
or in the musculature. Systemic infections may develop (Wolke 1975 ). Skin discoloration/fading and muscle lesions have been documented on neon tetra
( Paracheirodon innesi) (Michel et al. 2002 ). Gill lesions consist normally of yelloworange areas of necrosis. These start usually at the periphery of the gill, and extend
towards the base of the gill arch. Eventually, extensive erosion may completely
destroy the gill fi lament (Pacha and Ordal 1970 ). On the body, small lesions start as
areas of pale discoloration at the base of the dorsal fi n or occasionally at the base of
the pelvic fi n, and lead to deterioration of the fi ns. These areas increase in size and
may become as large as 3–4 cm in diameter, covering as much as 20–25 % of the
total surface area of the fi sh. This may have the characteristic appearance of a saddle, and hence the descriptive term, ‘saddleback’. Frequently, the skin becomes
completely eroded away, exposing the underlying muscle. Large numbers of bacteria are present at the advancing edge of the lesion. It is not uncommon for the fi sh
to die within 48 h of the appearance of the skin discoloration (Pacha and Ordal
1970 ; Becker and Fujiwaha 1978 ; Morrison et al. 1981 ).
Isolation
Cytophaga agar (Appendix in Chap. 12 ; after Anacker and Ordal 1959 ) and Bootsma
and Clerx’s medium for Fla. columnare (Appendix in Chap. 12 ; Bootsma and Clerx
1976 ) are useful for the recovery of the pathogen. Antibiotic-containing selective
7 Flavobacteria and Cytophagas
Flavobacterium columnare (=Flexibacter/Cytophaga
columnaris)
Characteristics of the Disease
Columnaris has been recognised to have worldwide distribution in a wide range of
freshwater fi sh, including Arctic charr, bass, black bullheads, carp, channel catfi sh,
chub, eel, goldfi sh, killifi sh, loach, perch, rainbow trout, roach, Atlantic salmon,
chinook salmon, sheatfi sh, squawfi sh, tilapia, white crappie, whitefi sh and whitesuckers (Nigrelli 1943 ; Nigrelli and Hutner 1945 ; Wakabayashi and Egusa 1966 ;
Ajmal and Hobbs 1967 ; Fijan 1969 ; Bowser 1973 ; Wobeser and Atton 1973 ; Chun
1975 ; Bootsma and Clerx 1976 ; Ferguson 1977 ; Farkas and Oláh 1980 ; Kuo et al.
1981 ; Morrison et al. 1981 ; Chen et al. 1982 ; Koski et al. 1993 ; Welker et al. 2005 ).
The disease was considered to be suffi ciently serious to warrant inclusion in the list
of notifi able fi sh diseases, as defi ned by the (British) Diseases of Fish Act, 1937.
However, columnaris was omitted from the 1983 Act.
Infection with Fla. columnare may result in several discrete disease conditions.
In young fi sh, there is often negligible pathology before death ensues. The gill is
usually the major site of damage. Typically, congestion (blockage) of the blood vessels supplying the gills occurs, with dissociation of the surface epithelium of the
lamellae from the capillary bed. There may be scattered areas of haemorrhaging
(Pacha and Ordal 1967 ). In adult fi sh, the lesions may occur on the gills, skin and/
or in the musculature. Systemic infections may develop (Wolke 1975 ). Skin discoloration/fading and muscle lesions have been documented on neon tetra
( Paracheirodon innesi) (Michel et al. 2002 ). Gill lesions consist normally of yelloworange areas of necrosis. These start usually at the periphery of the gill, and extend
towards the base of the gill arch. Eventually, extensive erosion may completely
destroy the gill fi lament (Pacha and Ordal 1970 ). On the body, small lesions start as
areas of pale discoloration at the base of the dorsal fi n or occasionally at the base of
the pelvic fi n, and lead to deterioration of the fi ns. These areas increase in size and
may become as large as 3–4 cm in diameter, covering as much as 20–25 % of the
total surface area of the fi sh. This may have the characteristic appearance of a saddle, and hence the descriptive term, ‘saddleback’. Frequently, the skin becomes
completely eroded away, exposing the underlying muscle. Large numbers of bacteria are present at the advancing edge of the lesion. It is not uncommon for the fi sh
to die within 48 h of the appearance of the skin discoloration (Pacha and Ordal
1970 ; Becker and Fujiwaha 1978 ; Morrison et al. 1981 ).
Isolation
Cytophaga agar (Appendix in Chap. 12 ; after Anacker and Ordal 1959 ) and Bootsma
and Clerx’s medium for Fla. columnare (Appendix in Chap. 12 ; Bootsma and Clerx
1976 ) are useful for the recovery of the pathogen. Antibiotic-containing selective
7 Flavobacteria and Cytophagas