Immunostimulants stimulate innate immune components mostly and the fish do rely more on the innate immunity to prevent from diseases. These immunostimulative substances mostly activate the phagocytes and their function along with production of acute phase proteins to render protection against diseases. Many such substances such as glucans, levamisole, chitin, lipopolysaccharides, lactoferrin, vitamins C and E, hormones, CpG-ODN and nucleotides have been reported to increase protection against bacterial, viral and parasitic diseases in fish.
