400
A causal mention was given initially to the role of Cyt. johnsonae and Cyt. rosea
as fi sh pathogens (Christensen 1977 ). Cyt. johnsonae has emerged as a problem in
Australia. However, only scant information is available about Cyt. rosea ; therefore,
this organism will not be considered further.
An organism was recovered initially from the gills of diseased hatchery-reared
salmon, trout and suckers in Michigan, USA (Strohl and Tait 1978 ). Thirteen isolates were recovered, and although similarities were noted to organisms previously
described by Borg ( 1960 ), Pacha and Porter ( 1968 ) and Anderson and Conroy
( 1969 ), it was decided to elevate them into a new species, as Cyt. aquatilis (Strohl
and Tait 1978 ), and thence to Fla. hydatis (Bernardet et al. 1996 ) . It must be emphasised that Strohl and Tait ( 1978 ) did not prove that the organisms were capable of
causing disease. Nevertheless, we have recovered similar organisms from outbreaks
of gill disease in farmed rainbow trout from England.
Cytophaga sp. has been associated with skin and muscle lesions on Atlantic
salmon in the U.S.A. (Kent et al. 1988 ), and a previously undescribed Cytophaga –
like bacterium (CLB) has been associated with a gill and systemic disease in turbot
(Mudarris and Austin 1989 ). This organism was described as a new species, as Fla.
scophthalmum (Mudarris et al. 1994 ), which was re-classifi ed to Chrys. scophthalmum (Vandamme et al. 1994 ).
Some new species have been recovered from diseased fi sh, but pathogenicity has
not been confi rmed. These include:
• Chrys. arothri was recovered from the kidneys of puffer fi sh ( Arothron hispidus )
caught off the coast of Hawaii (Campbell et al. 2008 ).
• Chrys. viscerum was described from the gill and liver of diseased rainbow trout
in Spain (Zamora et al. 2012a ).
• Chrys. oncorhynchi was described from the gills and liver of rainbow trout
(Zamora et al. 2012c ).
• Chrys. tructae was recovered from rainbow trout (Zamora et al. 2012d ).
• Chrys. shigense was recovered from diseased rainbow trout (Zamora et al.
2012e ).
Little is known about the role of Sporocytophaga as a fi sh pathogen. Mixed
infections attributed to Sporocytophaga and V. anguillarum occurred as surface
lesions, termed saltwater columnaris, on salmon and trout held in marine conditions
(Wood 1968 ). However, apart from discussing the presence of microcysts which
began to form at 2–7 days, there is little information about this suspected pathogen
(Pacha and Ordal 1970 ).
The precise reservoir of most of these fi sh pathogens remains unclear. Yellow
and orange-pigmented bacteria occur in large numbers in fresh water (Allen et al.
1983 ) and seawater (Austin 1982 ), and comprise part of the normal microfl ora of
gills of healthy salmonids (Trust 1975 ) and possibly even eggs (Hansen et al. 1992 ).
Therefore, it seems likely that the taxa comprising the fi sh pathogens occur naturally in the aquatic environment.
7 Flavobacteria and Cytophagas
A causal mention was given initially to the role of Cyt. johnsonae and Cyt. rosea
as fi sh pathogens (Christensen 1977 ). Cyt. johnsonae has emerged as a problem in
Australia. However, only scant information is available about Cyt. rosea ; therefore,
this organism will not be considered further.
An organism was recovered initially from the gills of diseased hatchery-reared
salmon, trout and suckers in Michigan, USA (Strohl and Tait 1978 ). Thirteen isolates were recovered, and although similarities were noted to organisms previously
described by Borg ( 1960 ), Pacha and Porter ( 1968 ) and Anderson and Conroy
( 1969 ), it was decided to elevate them into a new species, as Cyt. aquatilis (Strohl
and Tait 1978 ), and thence to Fla. hydatis (Bernardet et al. 1996 ) . It must be emphasised that Strohl and Tait ( 1978 ) did not prove that the organisms were capable of
causing disease. Nevertheless, we have recovered similar organisms from outbreaks
of gill disease in farmed rainbow trout from England.
Cytophaga sp. has been associated with skin and muscle lesions on Atlantic
salmon in the U.S.A. (Kent et al. 1988 ), and a previously undescribed Cytophaga –
like bacterium (CLB) has been associated with a gill and systemic disease in turbot
(Mudarris and Austin 1989 ). This organism was described as a new species, as Fla.
scophthalmum (Mudarris et al. 1994 ), which was re-classifi ed to Chrys. scophthalmum (Vandamme et al. 1994 ).
Some new species have been recovered from diseased fi sh, but pathogenicity has
not been confi rmed. These include:
• Chrys. arothri was recovered from the kidneys of puffer fi sh ( Arothron hispidus )
caught off the coast of Hawaii (Campbell et al. 2008 ).
• Chrys. viscerum was described from the gill and liver of diseased rainbow trout
in Spain (Zamora et al. 2012a ).
• Chrys. oncorhynchi was described from the gills and liver of rainbow trout
(Zamora et al. 2012c ).
• Chrys. tructae was recovered from rainbow trout (Zamora et al. 2012d ).
• Chrys. shigense was recovered from diseased rainbow trout (Zamora et al.
2012e ).
Little is known about the role of Sporocytophaga as a fi sh pathogen. Mixed
infections attributed to Sporocytophaga and V. anguillarum occurred as surface
lesions, termed saltwater columnaris, on salmon and trout held in marine conditions
(Wood 1968 ). However, apart from discussing the presence of microcysts which
began to form at 2–7 days, there is little information about this suspected pathogen
(Pacha and Ordal 1970 ).
The precise reservoir of most of these fi sh pathogens remains unclear. Yellow
and orange-pigmented bacteria occur in large numbers in fresh water (Allen et al.
1983 ) and seawater (Austin 1982 ), and comprise part of the normal microfl ora of
gills of healthy salmonids (Trust 1975 ) and possibly even eggs (Hansen et al. 1992 ).
Therefore, it seems likely that the taxa comprising the fi sh pathogens occur naturally in the aquatic environment.
7 Flavobacteria and Cytophagas