Immunostimulants: Towards Temporary Prevention of Diseases in Marine Fish

Due over the last years, marine aquaculture has grown into a very significant industry in many parts of the world, and in most developed countries marine fish are farmed intensively under conditions of high population density, infectious diseases pose a constant and highly cost threat to successful animal husbandry. Antibiotics provide a useful means of helping to control many bacterial diseases but there are many problems associated with the development of antibiotic resistance and recurrent outbreaks necessitating further, costly, treatments. Immunostimulants especially when administered through the diet have been perceived as potentially playing an important role in aquaculture. Efficiencies and strategic use of immunostimulation methods are presented and dose-effects between species analyzed. In addition, updated reviews of effects reported by several authors with nutritional and non-nutritional factors tested as immunostimulants in marine fish are presented; and those recent findings on the wide range of humoral and cellular innate immune responses affected by immunostimulation summarized. We conclude that actual knowledge of potential immunostimulants is still obscure in several aspects, especially in those related to pathways and mechanisms in which such substances can reach their specific cells targets. Nevertheless, immunostimulants as diet supplement, especially those of non-nutritional origin, should be good choice to induce a brief disease resistance enhancement in marine fish; although, methods and selected assess immune responses should be standardized between researchers in the aim of understanding better the complexity of disease resistance and immune function to make easier the development of these therapies until the production scale and not just as mare laboratory trials.