Scuticociliatosis is an economically important and frequently fatal disease of marine fish in aquaculture, affecting in particular turbot. There is one commercially available vaccine, but it only partially protects against one serotype of the parasite. To develop a universal vaccine against all serotypes and genotypes of the parasite, the genotypes and serotypes were identified. P. dicentrarchi isolates can be grouped into 4 genotypes and at least 3 different serotypes. Three families of proteins in P. dicentrarchi were identified that are likely to be protective antigens in fish, including variant-specific surface proteins (VSPs), leishmanolysins and ABC transporters. After being tested in a vaccination experiment in turbot, the best chimeric protein induced a relative percent survival of about 40%. Although the sequence of chimeric proteins must be optimized, these results suggest that the proteins are promising antigens for use in vaccines against P. dicentrarchi. The capacity of several gels as adjuvants was also tested, with chitosan and ulvan-chitosan gels, inducing a good immune response in turbot, which was similar to that induced by Montanide, but caused much less damage.