Vibrio salmoncida - Cold water vibriosis / Hitra disease

Introduction

Vibrio salmonicida is the causative agent of cold water vibriosis or so-called Hitra disease. During 2012 VESO Aqualab received several requests regarding outbreaks of this disease in northern Norway. We brushed the dust off our old challenge model, and further developed it into a clinically relevant bath challenge model. Mortality in control smolts typically reaches 70% and a new field isolate from northern Norway is available for challenge.

Challenge models to evaluate the effect of vaccination

Salmon parr (pre-smolts) are acclimatized for a minimum of one week before vaccination. After the immunization and smoltification period fish are challenged by i.p. injection or immersion in fresh water or sea water. After challenge, mortality is recorded during an observation period of two to four weeks. Evaluation of the potency of the vaccine is based on differences in mortality in vaccinated and unvaccinated fish.

Mortality in groups of unvaccinated salmon smolts bath challenged with Vibrio salmonicida.