Introduction

Bacteria belonging to the large family of Gram-negative bacteria Pasteurellaceae are the causative agents of pasteurellosis. The bacteria are capable of inducing clinical disease in several aquatic fish species, such as lumpfish and Atlantic salmon during the marine production phase.

The problem has escalated in recent years and a range of geno- and serotypes with different disease profiles have been described. VESO Aqualab has established challenge models in Atlantic salmon with Pasteurella isolated from recent field outbreaks in Norway and Scotland. The work has been done in close collaboration with Mowi and the Norwegian Veterinary Institute.

Challenge model

Atlantic salmon post-smolts are acclimatized for minimum two weeks in sea water before challenge by i.p. injection of bacteria at 15°C. Mortality is recorded during an observation period of 2-3 weeks.

Mortality in duplicate groups of unvaccinated Atlantic salmon post-smolts challenged by i.p. injection of Pasteurella sp. (Norwegian and Scottish strain).