Effects of the Immunomodulator<i>Ecteinascidia turbinata</i>Extract on<i>Edwardsiella ictaluri</i>Infection of Channel Catfish

Abstract

Ecteinascidia turbinate extract (Ete) dramatically decreased the survival of channel catfish Ictalurus punctatus that were challenged with a virulent strain of Edwardsiella ictaluri. A 0.625-μg or a 1.250-μg dose of Ete administered intraperitoneally 2 d before, on the same day, or 2 d after a 14-d LD50 dose (dose lethal to 50% of the test fish) of E. ictaluri decreased survival to 20% or less after 14 d. The extract significantly (P = 0.05) enhanced, by approximately 2.5-fold, the ability of adherent anterior kidney cells to phagocytize. However, Ete did not significantly affect antibody titers to E. ictaluri compared to those of control fish not treated with Ete. This study demonstrated that although immunoenhancement occurred in channel catfish injected with Ete, their ability to survive infection with E. ictaluri decreased.