Abstract
This study was undertaken to investigate the immune response of eel Anguilla japonica against formalin-killed cells (FKC) of Cytophaga columnaris. Eels were vaccinated by immersion or injection with FKC. The immune response of the eels was studied 2 weeks after the vaccination. Prior to the challenge, the eel skin was damaged by wiping with alcohol absorbed cotton. For the challenge, the fish were immersed in a suspension of C. columnaris at a density of 1.0 × 107 CFU/ml for 15 min.
The survival rates of the immersion, injection and control groups were 60, 20 and 0% respectively. In the immersion group skin lesions appeared later than in the other groups, and infiltration of leucocytes in skin lesions occurred at 12 h after the challenge, while no such leucocyte infiltration occurred in other groups. Inhibition activity of bacterial adhesion in the skin was demonstrated in the immersion fish. However, no agglutinating antibody was detectable in the serum or mucus of fish vaccinated by immersion. These results indicate that immersion immunization can activate the eel skin defense system.
