Susceptibility of juvenile and sub-adult Atlantic halibut (Hippoglossus hippoglossus L.) to infection by Vibrio anguillarum and efficacy of protection induced by vaccination

Experimental bath challenge of juvenile and sub-adult Atlantic halibut with Vibrio anguillarum induced severe mortalities of 47 and 80%, respectively. However, animals vaccinated with a commercial V. anguillarum vaccine demon strated excellent protection against the disease (100% RPS). This study als o describes the gross pathology and histological changes associated with th is infection. A loss of coordination, haemorrhage at the fin base and splen omegaly were frequent findings. Serum agglutinating activity demonstrated a rise following vaccination, the mean log, titre rising from 3.8 to 8.4. This was associated with a signifi cant rise in antibody-mediated complement killing ability of immune serum w hen compared to non-immune serum.