13 - Adjuvants and Immunostimulants for Potentiating Protection Against Furunculosis in Fish

Abstract

Effective bacterins against furunculosis disease in salmonids are now commercially available. The adjuvants are the substances having potentiating effects on the specific immune response and are used with vaccines. When these adjuvants are used without vaccine, these are termed as “immunostimulants.” The addition of adjuvant heightens the humoral antibody titres and enhances protection against furunculosis, that is, increases the effectiveness of bacterins used against furunculosis. Complete Freund's adjuvant (CFA) was used as the important potentiating component for the first time. Beta-glucans, muramyl dipeptide, streptococcal extracts, light-oils, and levamisole induce marked elevations of the non-specific defence mechanisms, as well as the specific immune response of fish. The immunostimulants affect the nonspecific defense mechanisms. The CFA when injected without a bacterin has the capability to induce significant protection against furunculosis. Nonspecific defense mechanisms, including phagocytic cell adherence, oxidative radical release, and engulfment, are among the most important early cellular factors in protection.