GLUCAN ADMINISTRATION POTENTIATES IMMUNE DEFENSE-MECHANISMS OF CHANNEL CATFISH, ICTALURUS-PUNCTATUS RAFINESQUE

Intraperitoneal injection of beta-1,3 glucan in channel catfish, Ictalurus punctatus Rafinesque, greatly reduces mortality from experimental infection with Edwardsiella ictaluri. Anterior kidney phagocytes from fish receiving glucan had enhanced phagocytic and bactericidal ability. The elevated bactericidal ability of phagocytes was not accompanied by increased production of hydrogen peroxide. Fish injected with glucan responded to subsequent E. ictaluri immunizations with higher serum antibody titres relative to the control catfish. The timing of glucan administration and antigen immunization was also important. These results indicate that beta-1,3 glucan potentially could be utilized prophylactically as an immunomodulator in channel catfish.