Pasteurella atlantica in Norwegian lumpsuckers : Characterisation, pathogenicity, vaccine development and immune responses

• Main Author: Ellul, Rebecca Marie
• Other Authors: orcid:0000-0003-1520-4017
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Bergen 2021
• Subjects: Norway; First Milestone; Atlantic salmon
• Online Access: https://hdl.handle.net/11250/2833271

Lumpsuckers (Cyclopterus lumpus L.) have gained popularity as a cleaner fish to biologically control salmon lice infestations in farmed Atlantic salmon in Norway. Starting in 2012, most producers in Norway have been raising lumpsuckers in captivity from milt and eggs collected from wild-caught fish. Since then, this industry has grown exponentially to meet the demands of Atlantic salmon producers. However, this growth was not without its issues. A number of bacterial diseases have been recorded from farmed lumpsuckers, with Pasteurella atlantica being one of the most concerning to farmers, given it is an emerging pathogen first diagnosed in Norwegian lumpsuckers in 2012. The main objectives of this project were to characterise P. atlantica, investigate the pathogenicity and the resulting immune responses in lumpsuckers, develop and test vaccines, and identify vaccine targets for future vaccine development. The first milestone was the establishment of P. atlantica culture in liquid medium. Through this work, bacterial growth was achieved in tryptic soy broth supplemented with foetal calf serum. This meant that bacteria could be produced in large volumes as required for experiments and vaccine development. Subsequently, a variety of challenge models were tested to study pathogenesis of P. atlantica in lumpsuckers. The bath challenge model was identified as the most reliable model, which could be further used during vaccine testing. Through these experiments, it was found that an asymptomatic carrier status occurs following exposure to the bacteria, highlighting the importance of fish health screening programs. To that end, whole cell inactivated vaccines were developed against P. atlantica to investigate their protection potential. However, only limited protection was conferred following experimental challenge of vaccinated lumpsuckers despite serology following vaccination showing high specific antibody levels. Additionally, in vitro experiments to investigate interactions between P. atlantica and lumpsucker head ...