Field Testing of Injected Vibrio anguillarum Bacterins in Pen-Reared Pacific Salmon

Abstract

I.p. injection of 3 types of V. anguillarum bacterin (heat-killed, formalin-killed, and heat and formalin-killed) was tested in chinook (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) to assess the feasibility of preventing vibriosis by immunization in commercial aquaculture. A single injection of V. anguillarum bacterin gave substantial protection to chinook salmon for 6 mo. postinoculation (32% mean mortality in all injected groups) compared to the control group (85% mortality). Chinook salmon showed the highest survival when treated with the heat-killed V. anguillarum bacterin. All groups of coho salmon had 7.0% mortality; immunization was not beneficial to survival. Serum antibody titer of V. anguillarum agglutinins was increased by i.p. injection. V. anguillarum was the pathogen most frequently isolated from moribund chinook salmon; Aeromonas salmonicida was the predominant organism isolated from moribund coho salmon.