Applications of Immunostimulants in Aquaculture: A Review

Abstract

Immunostimulants are valuable for the control of fish disease and may be useful to fish culture. The immunostimulatory effects on gulcan, chitin, lactoferrin and levamisole of fish and shrimp have been reported. Nutritional factors such as V sub(B), V sub(C), growth hormone and prolactin have also been reported to be immunostimulants. These immunostimulants mainly facilitate the function of phagocytic cells and increase their bactericidal activities. Serval immunostimulants also stimulate the natural killer cells, complement, lysozyme and antibody responses of fish. The activities of these immunological functions are associated with increasing the protection against infectious disease. Resistances to bacterial pathogens such as Vibio anguillarum, V. salmonicida, and Streptococcus sp. and to parasitic infections such as WSSV and Herpesvirus cyprini can be increased by administration of immunostimulants. Injecting administration of immunostimulants is the most effective method in using immunostimulants. Oral and immersion methods have also been reported, but the efficacies of these methods decreases with long-term administration. Overdoses of several immunostimulants have not been well-studied. In conclusion, immunostimulants can reduce the loss caused by disease in aquaculture; however, they may not effectively resist all diseases. For the effective use of immunostimulants, the timing, dosages, method of administration and the physiological condition of fish need to be taken into consideration.