Emerging role of immunostimulants in combating the disease outbreak in aquaculture

Abstract

The contribution of aquaculture to fish production is steadily increasing. Among various kinds of cultivated aquatic organisms, many marine and freshwater finfish and shellfish species constitute an important industry with their production increasing every year. Development of the aquaculture industry and increasing demand for fish production further provocate intensive fish culture, where the fish is at high risk of infectious disease caused by bacteria, virus, parasites etc. Use of expensive chemotherapeutants and antibiotics for controlling disease have widely been criticized for their negative impacts 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. Hence, instead of chemotherapeutic agents, increasing attention is being paid to the use of immunostimulants for disease control measures in aquaculture. Immunostimulants 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. An application of immunostimulants for the prevention of fish diseases are considered as an attractive and promising area. They mainly promotes the function of phagocytes and increase their microbicidal power. 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. This review article mainly considers the recent developments in this area to control fish diseases and enhance the growth of fish in the culture setups, and describing all different types and sources of immunostimulants, objective and evaluation of the mode of work.