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

Abstract

Intraperitoneal injection of three types of Vibrio anguillarum bacterin (heat-killed, formalin-killed, and a combination of 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) in comparison 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 less than 7.0% mortality, and immunization was not beneficial to survival. Serum antibody titer of V. anguillarum agglutinins was increased by intraperitoneal injection. Vibrio anguillarum was the pathogen most frequently isolated from moribund chinook salmon; Aeromonas salmonicida was the predominant organism isolated from moribund coho salmon.