Indrani Karunasagar, Iddya Karunasagar
Microbial diseases are a major problem for shrimp aquaculture in most parts of the world. In India, white spot baculovirus (WSBV) has been causing serious mortalities since 1994. In hatcheries, Vibrio infections also cause mass mortalities. By conventional microbiological and histopathological methods, it takes several days to arrive at a proper diagnosis. However DNA based methods such as polymerase chain reaction (PCR) enable rapid and sensitive detection of pathogens. In India PCR assay was tried for detection of Vibrio spp. and WSBV in shrimp. By this method, WSBV could be detected in apparently healthy larvae enabling farmers to choose virus free seeds for stocking. PCR could also detect virus in carrier animals such as crabs and pest prawns.
Laboratory studies indicate that immunostimulation of shrimp is possible through oral administration of immunostimulants. In field trials, animals treated with immunostimulants showed improved survival when there was attack by WSBV. In hatcheries, treatment of larvae by immersion appeared to improve survival from nauplii to post-larval stage.
Bioremediation of ponds by application of a bacterial consortium after +/- 60 days of culture helped in improving sediment quality, thus reducing the stress and consequent disease problems.
(UNESCO MIRCEN for Marine Biotechnology, Department of Microbiology, University of Agricultural Sciences, College of Fisheries, Mangalore-575 002, India)