New case study: ImmuLice - developing a new strategy against sea lice

The focus of this project was to explore the potential for a vaccine against sea lice.

Sea lice remain a challenge in Atlantic salmon farming. A range of pharmaceutical and biological treatments are available, although the potential for growing parasite resistance can reduce the effectiveness of traditional control methods. A vaccine would offer a sustainable, environmentally friendly solution that improves fish welfare and reduces reliance on chemical treatments. So far, no effective vaccine exists.

The ImmuLice project used a recombinant antigen called Cathepsin L (CatL), a gut protein in the parasite, to develop and test a vaccine for adult lice. Valued at £76k, the project partners were AquaTreck, University of Stirling, Moredun Research Institute and Moredun Scientific, and the project was supported by SAIC.

The work was divided into three stages:

• Produce the antigen: using a yeast-based system, researchers successfully created and purified large amounts of CatL protein, proving it could be made at scale for vaccine development.
• Formulate the vaccine: the protein was stabilised and combined with an adjuvant for injection, creating a reliable vaccine candidate.
• Test its effectiveness: a new challenge model was developed to expose vaccinated salmon to adult lice under realistic conditions, while monitoring immune responses and parasite behaviour.

Results showed that vaccinated fish produced antibodies against CatL, however there was no significant reduction in lice numbers or egg viability compared to controls. However, RNA sequencing revealed that lice feeding on vaccinated fish exhibited stress-related gene changes, suggesting the vaccine influenced parasite physiology. This insight opens new research avenues into how host immunity affects lice biology.

The project achieved major milestones: the creation of a scalable antigen production system, establishing an adult lice challenge model, and the development of analytical tools for studying host–parasite interactions. These provide a strong foundation for future work, including multi-antigen vaccines and improved formulations.

This project built on the work of an earlier SAIC-funded sea lice vaccine study.

The full title of this project is ‘Developing a recombinant gut antigen and evaluating its impact on adult sea lice: ImmuLice’.

Read the full case study