Vibriosis, the ubiquitous and autochthonous members of the estuary and shrimp culturing ponds and plays a vital role in reducing the general health conditions of commercially important shrimp. Drug resistant Vibrio spp. and antibiotic residues have become a global concern and there is a need to develop alternative strategies to control bacterial pathogens. Phage has been proposed as bacterial pathogen controlling agents in a process called phage therapy. Phage particles are natural inhabitant of ecosystem so there is no harm or environmental hazardous, while reintroduced into the same environment with enriched count.

The present study hypothesized that the phage therapy could be developed as an effective means to counteract infection and control V. parahaemolyticus in shrimp. Based on the previous experiments, we applied phages to V. parahaemolyticus in experimental tank. In this research we did two experiments to examine the efficacy of phages in controlling V. parahaemolyticus infection and immune response in shrimp.

In Experiment I, V. parahaemolyticus and phages (individual and cocktail) dispersed in water with shrimp.

Estimation of bacteria and phages count at every 12 h interval of time up to 96 h in water and calculation of shrimp mortality rate. In Experiment II, V. parahaemolyticus and phage particles (individual and cocktail) mixed with feed and fed to shrimp.

At every 24 h after phage feeding, monitoring immune response of shrimp like total haemocytes count (THC), total phenoloxidase activity, NBT assay (Respiratory Burst activity) and lysozyme activity.