GLUCAN INJECTION OR BATH EXPOSURE GIVEN ALONE OR IN COMBINATION WITH A BACTERIN ENHANCE THE NONSPECIFIC DEFENSE-MECHANISMS IN RAINBOW-TROUT(ONCORHYNCHUS-MYKISS)

Elevations in the non-specific defence mechanisms were noted after tro ut were injected or bathed in glucan solutions or in solutions contain ing the glucan combined with a bacterin, Y. ruckeri O-antigen. Periodi c non-lethal blood samples showed that neutrophil activity as evaluate d by the ability of the cells to stick to glass and produce oxidative radicals as detected by the nitroblue tetrazolium (NBT) assay, rose af ter treatments within 2 days. Elevated phagocytosis, assessed by incre ased uptake of glutaraldehyde-treated sheep red blood cells, also conf irmed these kinetics. The numbers of circulatory glass-adherent cells from fish given the glucans by injection or bath was twice the level o f the sham-treated controls; likewise the phagocytic ratio also was tw o-fold higher. In following the kinetics of the non-specific defensive responses, the injection of the glucan caused an immediate, slight re duction of NBT staining cells and numbers of leukocytes before the 2-3 day rise; this was not obvious in the fish given the glucan by bath. The glucans could play an important role in the prevention of diseases in fish culture.