Disease problem area major constraint for development of aquaculture. Biotechnological tools such as molecular diagnostic methods, use of vaccines and immunostimulants are gaining popularity for improving the disease resistance in fish and shellfish species world over for viral diseases, avoidance of the pathogen in very important.in this context there is a need to rapid method for detection of the pathogen. Biotechnological tools such as gene probes and polymerase chain reaction (PCR) are showing great potential in this area. Gene probes and PCR based diagnostic methods have developed for a number of pathogens affecting fish and shrimp. In case of finfish aquaculture, number of vaccine against bacteria and viruses has been developed.
Some of these have been conventional vaccines consisting of killed microorganism but new generation of vaccine consisting of protein subunit vaccine genetically engineered organism and DNA vaccine are currently under development. In the vertebrate system, immunization against disease is a common strategy. However the immune system of shrimp is rather poorly developed, biotechnological tools are helpful for development of molecule, which can stimulate this immune system of shrimp. Recent studies have shown that the non-specific defense system can be stimulated using, microbial product such as lipopolysacharides, peptidoglycans or glucans. Among the immunostimulants known to be effective in fish glucan and levamisole enhance phagocytic activities and specific antibody responses.