External & Internal Signs

Clinical Signs

External Symptoms: 

Affected shrimp gather in shallow water and at the edges of the tank/pond, are inactive and anorexic and will eventually die, floating to the surface. 
Melanised shell lesions and/or tail rot. 
Darkening or reddening of the body. 
Discolouration of the gills is also seen.

Laboratory Tests

Bacteriology: 
Inoculation of infected tissue or hemolymph on NaCl-enriched media such as TCBS, TSA and BHIA. 

Further identification of the obtained and purified bacterial strains needs to be carried out using, for example, a biochemical reaction profile (like API), gel electrophoresis of purified LPS or DNA extracts, or slide agglutination tests using specific antibodies.

Post Mortal Diagnosis

Internal Symptoms: 
The hepatopancreas is pale but dark areas (melanised tubules) can be observed.
Melanised areas on the gills.
Cuticular lesions infiltrating into the muscle showing necrosis (opaque areas). 

Histopathology
Cuticular areas (exoskeleton and/or the lining of the oesophagus and stomach) that are colonised by the bacteria show necrosis followed by haemocytic infiltration and melanisation. 

Infection of the hepatopancreas shows a severe haemocytic encapsulation of the bacterial colonies filling the tubular lumen.