Acquired Protection against Neobenedenia girellae in Japanese Flounder.

Abstract

The immune response of Japanese flounder (Paralichthys olivaceus) against Neobenedenia girellae (Hargis, 1955) (Monogenea : Capsalidae) was investigated. An acquired protection of fish against secondary infection with the parasite was demonstrated by a reduction in the number and body size of parasites on primed fish which had previously been infected with N. girellae and treated by freshwater bath. In the same experiment, however, no raise in the level of antibody in the sera of primed fish was detected by the enzyme-linked immunosorbent assay (ELISA). In another experiment, although antibody was detected by ELISA in the sera of fish immunized by injection with sonicated parasite antigen, there was no significant difference in the parasite counts between antigen-injected and PBS-injected control fish when challenged with oncomiracidia of N. girellae. These results indicate that the protection induced by the previous infection was not associated with the humoral antibody.