, Diagnosis an-&& of Shrimp Diseases - Central Institute of ...

BACTERIAL AND FUNGAL DISEASES OF SHRIMPS.V. AlavandiThe bacteria causing diseases of penaeid shrimp constitute part of the natural microbialflora of seawater. Accumulation of un-utilized feed and metabolites of shrimp in the culturetanks1 ponds enrich the water with organic matter that supports the growth and multiplicationof bacteria and other microorganisms. Bacterial infections of shrimp are primarily stressrelated. Adverse environmental conditions or mechanical injuries are important predisposingfactors of bacterial infection; and disease. The most common shrimp pathogenic bacteriabelong to the genus Yibrio. Other Gram-negative bacteria such as Aeromonas spp.,Pseudomonas spp., and Flavobacterium spp., are also occasionally implicated in shrimpdiseases.Bacterial Septicaemia (Vibrio disease)Signs and Symptoms: This is one of the severe systemic diseases caused by bacteria. Theaffected shrimps are lethargic and show abnormal swimming behaviour. The periopods andpleopods may appear reddish due to expansion of chromatophores and the shrimps may showslight flexure of the abdominal musculature. In severely affected shrimps the gill coversappear flared up and eroded. In more severe cases extensively melanised black blisters can beseen on the carapace and abdomen.Cause: Bacteria such as Yibrio alginolyficus, V. anguillarunz, K parahaemolyticws, VibrioSPP-Diagnosis: The bacterial septicaemia or systemic vibriosis is diagnosed based on the grosssigns and syinptoms, and confirmed by isolation of pathogen fiom haemolymph by standard~nicrobiological methods and histopathology.Preverztion: Maintain good water quality and reduce the organic load by increased waterexchange.Control: Increase water exchange with good quality seawater. Feed shrimps with antibioticfortified feeds (only after ascertaining in-vitro sensitivity of the pathogen). e.g., feedscontaining oxytetracycline @ 1.5g /Kg, fed at 2-10% of body weight for 10-14 days alongwith proper water and pond management. Sufficient withdrawal period (about 25 - 30 days)should be aIlowed for the antibiotic to become inactive or harmless.