Application of immunostimulants as an alternative to vaccines for health management in aquaculture

Aquaculture, one of the fastest growing food producing sectors, is gaining momentum in several parts of the world. Diseases in fish constitute one of the most important problems and challenges for aquaculturists. Hence, aquaculturists undertake good management practices to ensure the production of healthy fish. Intensification has become a common practice in both finfish and shellfish culture to optimize the returns. High stocking densities, artificial feeding and fertilization have become common husbandry practices in carp culture systems. Due to intensification of culture practices, diseases in rearing of fishes have become major threat to the sustainability of aquaculture industry. Use of synthetic chemicals and antibiotics has been partially successful in preventing or treating fish diseases. Vaccination is an important tool in preventing infectious disease in humans and animals and both passive and active vaccinations are extensively employed in fish. A vaccine targets the specific immune response. It requires primary challenge with antigen and is dependent upon the clonally derived lymphocytes subsets to be implemented. Vaccines against some specific pathogens have been developed recently against some particular diseases. Thus, an alternative approach to boost or stimulate the innate immune system of farmed fish is an application of immunostimulants. Immunostimulants are considered as attractive and promising agents for prevention of diseases in fish and shellfish. In recent years, the proven beneficial effects of immunostimulants in many living systems promote their application for disease management in aquaculture practices.