~ 153 ~ International Journal of Fisheries and Aquatic Studies 2014; 2(1): 153-156 ISSN: 2347-5129 IJFAS 2014; 2(1): 153-156 © 2013 IJFAS www.fisheriesjournal.com Received: 12-08-2014 Accepted: 29-08-2014 Shyam Narayan Labh Aquaculture Research Lab, Central Department of Zoology Tribhuvan University, Kathmandu, Nepal Shubha Ratna Shakya Aquaculture Research Lab, Central Department of Zoology Tribhuvan University, Kathmandu, Nepal Correspondence: Shubha Ratna Shakya Aquaculture Research Lab, Central Department of Zoology Tribhuvan University, Nepal Email: shubharatnashakya@gmail.com Application of immunostimulants as an alternative to vaccines for health management in aquaculture Shyam Narayan Labh and Shubha Ratna Shakya Abstract 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. Keywords: Immunostimulants; Immune system; Aquaculture, Vaccine, fish 1. Introduction Aquaculture has been growing rapidly for food production in the last few decades. Several commercial fish species have been cultured intensively in narrow or enclosed spaces such as ponds, cages or tanks under overcrowding or high density conditions, thereby causing adverse effect on their health with a potentially stressful environment and infectious diseases [1] . The outbreaks of infectious disease in cultured fish have emerged as constraints for the development of aquaculture. These occurrences have spread through the uncontrolled movement of live aquatic animals resulting in the transfer of pathogenic organisms among countries [2] . Antibiotics and chemotherapeutics have been used to prevent or control bacterial infections in aquaculture for about 20 years [3] . Unfortunately, antibiotics treatment is not successful and sustainable due to increase antibiotic-resistant in bacteria, negative effects on the indigenous microflora of juveniles or adult fish [4] , accumulation of antibiotic residues in fish tissue and environment causing human and animal health issues. Vaccination is an effective prophylactic treatment for infectious diseases in fish culture, but it may be very expensive and stressful to the fishes. A single vaccine is effective against only one specific type of pathogen, but limits the effectiveness for wide range of pathogens due to the complex antigenic structure [5] . Therefore, eco-friendly disease-preventive alternative techniques have to be taken into account. One such promising alternative technique to strengthen fish immune systems is the application of immunostimulants in aquaculture [1] . 1.1 Concept of Immunostimulant Immunostimulants, also known as immunostimulators, are substances comprising of drugs and nutrients that activate the immune system by increasing activity of any of its components.