29
Characteristics of the Disease
According to Ross and Toth ( 1974 ), the abdomen of moribund fi sh were distended
because of the presence of ascitic fl uid. However, it was readily admitted that mortalities could not be directly attributed to the lactobacillus “pathogen”. The subsequent report of Cone ( 1982 ) indicated that the condition was stress mediated, insofar
as it was recognised mostly in post-spawning fi sh. In these specimens, there was an
accumulation of ascitic fl uid in the peritoneal cavity, and extensive damage in the
liver, kidney and spleen. Fin rot and other external signs of disease were absent.
However, petechial haemorrhages in the muscle and hyperaemic air bladder were
observed in some fi sh. The heart and gills appeared normal. According to Hiu et al.
( 1984 ), the disease occurred in fi sh >1 year old, which may have undergone stress,
namely handling and spawning. Disease symptoms were varied, including septicaemia, the abdomen distended with ascitic fl uid, muscle abscesses, blood blisters just
beneath the skin, and internal haemorrhaging.
Isolation
The use of TSA or BHIA with incubation at 22–24 °C for 48 h has been advocated
(Ross and Toth 1974 ; Cone 1982 ; Hiu et al. 1984 ).
Characteristics of the Pathogen
There have been only a few reports citing Lactobacillus spp. as fi sh pathogens. The
initial work was by Ross and Toth ( 1974 ), who described mortalities among 3-year old
rainbow trout in a hatchery in California. The term pseudokidney disease was coined
by these workers to distinguish the condition from BKD. However, it is not clear what
pathological signifi cance, if any, could be attributed to the lactobacilli, because pure
cultures were incapable of reproducing infection. Nevertheless, lactobacilli were again
implicated in an infection of female 2–3 year old rainbow trout from a hatchery in
Newfoundland, Canada (Cone 1982 ), but this was a mixed bacterial infection involving
primarily lactobacilli and also Aer. hydrophila, Ps. fl uorescens and Enterobacteriaceae
representatives. There is no report about any pathogenicity experiments using the
Canadian Lactobacillus strain; therefore, its precise role as a fi sh pathogen is open to
question. Additional lactic-acid producing organisms have been isolated from the kidneys of moribund rainbow trout (B. Austin, unpublished data). Moreover, these isolates produced clinical disease upon intraperitoneal injection into salmonids. Similar
isolates have been studied by Professor Stemke (personal communication).
Hiu et al. ( 1984 )) proposed a new species, namely Lactobacillus piscicola, to
accommodate a group of 17 isolates recovered from diseased chinook salmon, cutthroat trout and rainbow trout. Similar isolates were recovered from juvenile salmonids and carp in Belgium and France (Michel et al. 1986 ) and from striped bass and
catfi sh in the U.S.A. (Baya et al. 1991 ). Then, Lactobacillus piscicola was reclassifi ed as Carnobacterium piscicola (Collins et al. 1987 ). In addition, fi shLactic Acid Bacteria
Characteristics of the Disease
According to Ross and Toth ( 1974 ), the abdomen of moribund fi sh were distended
because of the presence of ascitic fl uid. However, it was readily admitted that mortalities could not be directly attributed to the lactobacillus “pathogen”. The subsequent report of Cone ( 1982 ) indicated that the condition was stress mediated, insofar
as it was recognised mostly in post-spawning fi sh. In these specimens, there was an
accumulation of ascitic fl uid in the peritoneal cavity, and extensive damage in the
liver, kidney and spleen. Fin rot and other external signs of disease were absent.
However, petechial haemorrhages in the muscle and hyperaemic air bladder were
observed in some fi sh. The heart and gills appeared normal. According to Hiu et al.
( 1984 ), the disease occurred in fi sh >1 year old, which may have undergone stress,
namely handling and spawning. Disease symptoms were varied, including septicaemia, the abdomen distended with ascitic fl uid, muscle abscesses, blood blisters just
beneath the skin, and internal haemorrhaging.
Isolation
The use of TSA or BHIA with incubation at 22–24 °C for 48 h has been advocated
(Ross and Toth 1974 ; Cone 1982 ; Hiu et al. 1984 ).
Characteristics of the Pathogen
There have been only a few reports citing Lactobacillus spp. as fi sh pathogens. The
initial work was by Ross and Toth ( 1974 ), who described mortalities among 3-year old
rainbow trout in a hatchery in California. The term pseudokidney disease was coined
by these workers to distinguish the condition from BKD. However, it is not clear what
pathological signifi cance, if any, could be attributed to the lactobacilli, because pure
cultures were incapable of reproducing infection. Nevertheless, lactobacilli were again
implicated in an infection of female 2–3 year old rainbow trout from a hatchery in
Newfoundland, Canada (Cone 1982 ), but this was a mixed bacterial infection involving
primarily lactobacilli and also Aer. hydrophila, Ps. fl uorescens and Enterobacteriaceae
representatives. There is no report about any pathogenicity experiments using the
Canadian Lactobacillus strain; therefore, its precise role as a fi sh pathogen is open to
question. Additional lactic-acid producing organisms have been isolated from the kidneys of moribund rainbow trout (B. Austin, unpublished data). Moreover, these isolates produced clinical disease upon intraperitoneal injection into salmonids. Similar
isolates have been studied by Professor Stemke (personal communication).
Hiu et al. ( 1984 )) proposed a new species, namely Lactobacillus piscicola, to
accommodate a group of 17 isolates recovered from diseased chinook salmon, cutthroat trout and rainbow trout. Similar isolates were recovered from juvenile salmonids and carp in Belgium and France (Michel et al. 1986 ) and from striped bass and
catfi sh in the U.S.A. (Baya et al. 1991 ). Then, Lactobacillus piscicola was reclassifi ed as Carnobacterium piscicola (Collins et al. 1987 ). In addition, fi shLactic Acid Bacteria