This is one of the severe systemic disease caused by bacteria. The affected shrimps are lethargic and show abnormal swimming behaviour. The pereopods are pleopods may appear reddish due to expansion of chromatophores and the shrimps may show slight fexure of the abdominal musculature. In severly affected shrimp, the gill covers appear flared up and eroded. In more severe cases, extensively melanised black blisters can be seen on the carapace/abdomen.  

CAUSES  

Bacteria such as Vibrio alginolyticus, V. anguillarum, or V. parahaemolyticus.  

DIAGNOSIS  

Based on gross signs and symptoms and confirmed by isolation of pathogen from haemolymph by standard microbiological methods and histopathology.  

PREVENTION  

Maintain good water quality and reduce the organic load by increased water exchange.  

CONTROL  

Increase water exchange with good quality seawater. Feed shrimps with antibiotic fortified fees 9only after ascertaining in-vitro sensitivity of the pathogen), e.g. feeds containing oxytetracycline @ 1.5g/Kg, fed at 2-10% of body weight for 10-14 days along with proper water and pond management. Sufficient withdrawl period (about 25-30 days) should be allowed for the antibiotic to become inactive or harmless.