Occurrence of a motile Aeromonas Septicaemia in the imported ornamental fish, oscar (Astronotus ocellatus): Isolation, characterization and pathogenicity

A bacterial septicaemia occurred in 3-female oscars (Astronotus
ocellatus) of about 2-year old held in 300l freshwater aquaria in
south Tehran. The external signs of infected fish consisted of
lethargy, anaemia, distension (clinical dropsy), exophthalmia and
cataract. Internally there was a large amount of red-ascitic fluid
accumulated in the abdominal cavity with haemorrhages/
hyperaemia of internal organs, in particular, liver kidney,
peritoneum as well as the presence of dark-brown dots on the
surface of liver. Kidney was enlarged and undergone liqufactive
necrosis. The bacterio logical examination resulted in isolation of
single and pure Gram negative rod bacterium in which biochemical
and physiological characters resembles of Aeromonas veronii
biovar sobria. Experimentally, this isolate was relatively virulent to
goldfish of 2-5g at 20-23C. More details of condition such as
histopathological features and possible predisposing factors are
given in the text.