Immunostimulants: The best alternative to vaccination and antibiotics in aquaculture
AbstractImmunostimulants comprise a group of biological and synthetic compounds that enhance the non-specific cellular and humoral defense mechanism in animals. These substances such as levamisole and glucan, peptidoglycon, chitin, chitosan, yeast and vitamin combinations as well as various products derived from plants and animals are effective in prevention of diseases. Use of expensive chemotherapeutants and antibiotics for controlling disease have widely been criticized for their negative impact like residual accumulation in the tissue, development of the drug resistance and immunosuppression, thus resulting in reduced consumer preference for food fish treated with antibiotics (Anderson,1992). Hence, instead of chemotherapeutic agents, increasing attention is being paid to the use of immunostimulants for disease control measures in aquaculture. The use of immunostimulants for the prevention of fish diseases is considered an attractive and promising approach. These immunostimulants mainly promote the function of phagocytes and increase their microbicidal power. They also enhance production of acute phase proteins that trigger the innate defence mechanism of the host. However, a controversy exists over the use of these substances, as in a few cases they have failed to render enhanced protection or increase in immunity. Long-term exposure, over and under dosing problems, timing and method of application of these substances are discussed here. This review article mainly considers the recent developments in this area to control fish diseases describing all different types and sources of immunostimulants, their characteristics, objective and evaluation of the mode of work.
Key words: Immunostimulants, disease control, alternative, fish, antibiotics, aquaculture