IDENTIFICATION AND OCCURRENCE OF Vibrio parahaemolyticus IN SHRIMP PONDS OF SELECTED PONDS IN PONNERI, TIRUVALLUR DISTRICT

The present study aimed to monitor the occurrence of Vibrio parahaemolyticus, an opportunistic prawn pathogen, in two white-leg shrimp Litopenaeus vannamei culture ponds (from stocking to harvesting period), each located in the villages Pullikulam and Kumarasirulapakkam of Thiruvallur District. They were selectively isolated, counted using serial dilution and confirmed by 16s rDNA sequencing. Our study showed that V. parahaemolyticus occupied one tenth of the total microbial load in the ponds. The count ranged from 1000 to 1600 CFU/ml in water at the time of stocking and varied with time period. The sediment always harbour more bacteria than water and the number would reach up to 35×104 CFU/g in the harvesting period. Both the ponds showed a steep increase on the 30th day of stocking and then there is a gradual decrease or increase in the water parameter. The occurrence of the bacteria was found to depend on the water and soil quality parameters that vary with timelines. The study showed that the bacterial count increased with the culture periods in both the ponds. This would serve to be an indirect evaluation for the health assessment of the shrimps and raises the need for continuous validation on their loads.