107
sequencing of the 16S rRNA gene (homology = >99.9 % to Aerococcus viridans)
(Ke et al. 2012 ).
Pathogenicity
Two isolates were injected intraperitoneally (3.0 × 10
6 CFU/fi sh) and administered
by bathing (2 h in 1.5 × 10
7 CFU/ml) to tilapia leading to mortalities (85 % and 45 %,
respectively) with signs similar to those observed on the affected fi sh farm (Ke et al.
2012 ).
Bacillaceae Representatives
Bacillus spp.
Characteristics of the Disease
The initial outbreak of disease during 1989–1991 led to mortalities of 10–15 % of
farmed populations of Clarias carpis, Clarias gariepinus, Clarias nigrodigitatus,
‘Heteroclarias’ and Heterobanchus bidorsalis in Nigeria (Oladosu et al. 1994 ).
Diseased fi sh were characterised by weakness, lethargy, emaciation and generalised
necrotising dermatitis, with death occurring in a few days. Blood tinged fl uid was
present in the peritoneal cavity. Petechia and focal necrosis was evident in the liver
and kidney. The spleen was enlarged, soft and friable. The myocardium was
described as soft and fl abby. The stomach was hyperaemic (Oladosu et al. 1994 ).
Gram-positive rods of 1–4 μm in length were observed. It should be emphasised that
skin lesions revealed the presence of Aeromonas and Fla. columnare.
Bacillary necrosis was described in farmed populations of catfi sh (Pangasius
hypophthalmus) from the Mekong Delta, Vietnam. Mortalities among fi sh that did
not otherwise respond to treatment were observed, and the disease signs centred on
1–3 mm diameter white necrotic and granulomatous areas in the kidney, liver,
spleen and viscera. Apart from the presence of mostly myxosporean parasites, an
organism considered as an unspeciated Bacillus was recovered (Ferguson et al.
2001 ).
Isolation
Oladosu et al. ( 1994 ) relied on nutrient agar and incubation at the comparatively
high temperature of 37 °C for an unspecifi ed period to isolate Bacillus spp.
Bacillaceae Representatives
sequencing of the 16S rRNA gene (homology = >99.9 % to Aerococcus viridans)
(Ke et al. 2012 ).
Pathogenicity
Two isolates were injected intraperitoneally (3.0 × 10
6 CFU/fi sh) and administered
by bathing (2 h in 1.5 × 10
7 CFU/ml) to tilapia leading to mortalities (85 % and 45 %,
respectively) with signs similar to those observed on the affected fi sh farm (Ke et al.
2012 ).
Bacillaceae Representatives
Bacillus spp.
Characteristics of the Disease
The initial outbreak of disease during 1989–1991 led to mortalities of 10–15 % of
farmed populations of Clarias carpis, Clarias gariepinus, Clarias nigrodigitatus,
‘Heteroclarias’ and Heterobanchus bidorsalis in Nigeria (Oladosu et al. 1994 ).
Diseased fi sh were characterised by weakness, lethargy, emaciation and generalised
necrotising dermatitis, with death occurring in a few days. Blood tinged fl uid was
present in the peritoneal cavity. Petechia and focal necrosis was evident in the liver
and kidney. The spleen was enlarged, soft and friable. The myocardium was
described as soft and fl abby. The stomach was hyperaemic (Oladosu et al. 1994 ).
Gram-positive rods of 1–4 μm in length were observed. It should be emphasised that
skin lesions revealed the presence of Aeromonas and Fla. columnare.
Bacillary necrosis was described in farmed populations of catfi sh (Pangasius
hypophthalmus) from the Mekong Delta, Vietnam. Mortalities among fi sh that did
not otherwise respond to treatment were observed, and the disease signs centred on
1–3 mm diameter white necrotic and granulomatous areas in the kidney, liver,
spleen and viscera. Apart from the presence of mostly myxosporean parasites, an
organism considered as an unspeciated Bacillus was recovered (Ferguson et al.
2001 ).
Isolation
Oladosu et al. ( 1994 ) relied on nutrient agar and incubation at the comparatively
high temperature of 37 °C for an unspecifi ed period to isolate Bacillus spp.
Bacillaceae Representatives