Biocontrol of Bacterial Pathogens in Aquaculture with Emphasis on Phage Therapy

Loss due to diseases is a major problem in both shrimp farm and hatcheries and to control diseases, a number of antibiotics, sanitisers and chemicals are being used. This results in adverse environmental effects, emergence of antibiotic resistance and persistence of chemical residues in animal tissues. Considering the negative impact of antibiotics and other chemotherapeutants, biological control of pathogens would be a very useful strategy to prevent diseases in aquaculture and in this context, we looked into the potential for biocontrol of the shrimp pathogen, Vibrio harveyi which causes luminous bacterial disease in hatcheries and farms. A number of Bacillus spp were screened for their ability to produce anti-vibrio compounds. Several strains of B. megaterium, B. licheniformis, B. coagulans, B. circulans isolated from shrimp farm environments showed anti-vibrio activity. Bacteriophages capable of lysing several V. harveyi strains were isolated from shrimp culture environments and were found to be very efficient in reducing levels of V. harveyi in seawater microcosms. Application of bacteriophages to control luminous bacterial disease in shrimp hatcheries resulted in reduction of V. harveyi counts in water and in larvae and tremendously improved larval survival. The results show the potential of bacteriophages for therapy of luminous bacterial disease in aquaculture systems.