External & Internal Signs

Clinical Diagnosis

External symptoms

  • Swimming belly-up or on the side.
  • Distended abdomen
  • Slightly protruded red vent
  • Occasionally, small haemorrhages around the base of the fins

Laboratory Tests

Bacteriology:
Samples from brain, kidney, liver and spleen tissues plated on standard, non-selective TSA or BHIA media supplemented with NaCl or MA, incubated at 15 to 20 °C for 3 - 5 days might show small, translucent colonies. These colonies, which are 'sticky', can further be identified using classical identification tests. P. anguilliseptica is a Gram-negative long slender rod which is oxidase and catalase positive, non- fermentative and doesn’t require NaCl for growth. The motility is temperature and magnesium dependent. The organism is fairly non-reactive and will score negative on most phenotypic tests.

Post Mortal Diagnosis

Gross Lesions

  • Distended intestine filled with clear fluid
  • Ascitic fluid in abdominal cavity
  • Distended gall bladder
  • Pale liver with occasional blood-shot areas
  • Enlarged spleen

Histopathology:
Except for a non-specific inflammatory reaction in the internal organs, no particular features are seen in routine haematoxylin-eosin stain. Modified Gram’s stain shows the presence of rod-shaped bacteria in the infected organs.