620
Neisseriaceae Representative
Aquaspirillum sp.
There has been a report of putative Aquaspirilllum sp., along with Aer. hydrophila,
Pseudomonas sp. and Streptococcus sp., being associated with a disease, termed
epizootic ulcerative syndrome, in snakeheads and catfi sh obtained from two fi sh
farms in Thailand (Lio-Po et al. 1998 ). However, the evidence for the involvement
of Aquaspirillum is not convincing.
Slight lesions were reported to occur after 24 h of infection in experimental fi sh
(Lio-Po et al. 1998 ). This limited pathology casts doubt on the role of the organism
as a fi sh pathogen. Perhaps, synergism with Aer. hydrophila, Pseudomonas sp. and
Streptococcus may occur. Alternatively, Aquaspirillum may be an opportunistic
invader or saprophyte living on diseased tissue.
Lio-Po et al . ( 1998 ) used TSA supplemented with 10 % (v/v) horse serum and
cytophaga agar at an unspecifi ed temperature and duration to recover Aquaspirillum,
Aer. hydrophila and Streptococcus from diseased animals.
Oxalobacteraceae Representative
Janthinobacterium lividum
Characteristics of the Disease
During 1991, purple-pigmented Gram-negative rod-shaped bacteria were associated with mortalities at two fi sh farms. At one site in Scotland, moribund rainbow
trout (size range = 0.5–1.0 g) were diagnosed with RTFS. The second site in Northern
Ireland also experienced high mortalities (~35 % of the stock) in rainbow trout fry
of 0.2–0.5 g in size, 2–3 weeks after the introduction of feeding. At this site, the rise
in mortalities coincided with a change from the use of spring to river water (Austin
et al. 1992 ). In addition during January 1992, we found similar purple-pigmented
bacteria to be associated with skin lesions, on larger rainbow trout (100–200 g in
weight), which were otherwise debilitated with ERM. It is relevant to note that this
fi sh population had received prolonged and varied chemotherapy.
Small fi sh, considered to be displaying RTFS, became lethargic, displayed
exophthalmia, pale gills, enhanced skin pigmentation, swollen abdomen and (sometimes) skin lesions. Internally, the kidney was swollen, the spleen was pale and
elongated, and some ascitic fl uid was present in the peritoneal cavity (Austin et al.
1992 ). On the larger rainbow trout, the organism was associated with surface
lesions. In particular, the skin was sloughed-off along the entire fl ank of the animals,
from operculum to tail, exposing the underlying (necrotic) muscle.
11 Miscellaneous Pathogens
Neisseriaceae Representative
Aquaspirillum sp.
There has been a report of putative Aquaspirilllum sp., along with Aer. hydrophila,
Pseudomonas sp. and Streptococcus sp., being associated with a disease, termed
epizootic ulcerative syndrome, in snakeheads and catfi sh obtained from two fi sh
farms in Thailand (Lio-Po et al. 1998 ). However, the evidence for the involvement
of Aquaspirillum is not convincing.
Slight lesions were reported to occur after 24 h of infection in experimental fi sh
(Lio-Po et al. 1998 ). This limited pathology casts doubt on the role of the organism
as a fi sh pathogen. Perhaps, synergism with Aer. hydrophila, Pseudomonas sp. and
Streptococcus may occur. Alternatively, Aquaspirillum may be an opportunistic
invader or saprophyte living on diseased tissue.
Lio-Po et al . ( 1998 ) used TSA supplemented with 10 % (v/v) horse serum and
cytophaga agar at an unspecifi ed temperature and duration to recover Aquaspirillum,
Aer. hydrophila and Streptococcus from diseased animals.
Oxalobacteraceae Representative
Janthinobacterium lividum
Characteristics of the Disease
During 1991, purple-pigmented Gram-negative rod-shaped bacteria were associated with mortalities at two fi sh farms. At one site in Scotland, moribund rainbow
trout (size range = 0.5–1.0 g) were diagnosed with RTFS. The second site in Northern
Ireland also experienced high mortalities (~35 % of the stock) in rainbow trout fry
of 0.2–0.5 g in size, 2–3 weeks after the introduction of feeding. At this site, the rise
in mortalities coincided with a change from the use of spring to river water (Austin
et al. 1992 ). In addition during January 1992, we found similar purple-pigmented
bacteria to be associated with skin lesions, on larger rainbow trout (100–200 g in
weight), which were otherwise debilitated with ERM. It is relevant to note that this
fi sh population had received prolonged and varied chemotherapy.
Small fi sh, considered to be displaying RTFS, became lethargic, displayed
exophthalmia, pale gills, enhanced skin pigmentation, swollen abdomen and (sometimes) skin lesions. Internally, the kidney was swollen, the spleen was pale and
elongated, and some ascitic fl uid was present in the peritoneal cavity (Austin et al.
1992 ). On the larger rainbow trout, the organism was associated with surface
lesions. In particular, the skin was sloughed-off along the entire fl ank of the animals,
from operculum to tail, exposing the underlying (necrotic) muscle.
11 Miscellaneous Pathogens