Diseases due to bacterial, viral, parasitic or fungal infections have historically been one of the main limiting factors to industrial-scale food production, and fish-farming represents no exception. Effective vaccination may mitigate losses, but vaccine development requires detailed knowledge about the infectious agents involved.

Species determination of microbial agents during routine diagnostics often relies on relatively crude molecular and/or phenotypical characterization tools. While facilitating fast and cheap identification, these tools often fall short when it comes to differentiating closely related strains of the same species. Methods offering higher resolution are thus needed for elucidating the population structure and epizootiology of such organisms, which may in turn be highly relevant for development of vaccine strategies.

While some ‘old-fashioned’ phenotypic tools such as serotyping still remain in wide use, the tremendous advances in sequencing technology during the last 10-20 years have prompted a gradual shift in favor of molecular methods. Molecular typing techniques allow for extremely detailed strain description, potentially enabling separation of isolates differing in only a single DNA/RNA residue.

The Fish Health Research Group is involved in various projects involving pathogen discovery, pathogen characterization, population genetics and pathogen ecology and evolution.