The significance of bacteria in the occurrence of water moulds, and the detection of water moulds and bacteria through PCR methods


Water moulds are widespread fungus-like microbes, oomycetes, living in freshwaters. Especially the Saprolegnia sp. cause serious problems in salmonid farming worldwide. In addition, mass mortalities of wild salmonids have been described, presumably caused by water moulds. At the moment, there are no sufficiently effective treatment methods or fast diagnostics, that is accurate detection methods for water moulds, which complicates its control and treatment. Very little is also known about the virulence of water moulds.

The initiative will explore the genotypes of water mould strains collected in Finland. The impact of bacteria isolated from fish on the virulence of water moulds will be investigated by means of experimental and field studies. Based on this data, PCR analytics will be developed for analysing the genotypes of water mould strains typical to Finland and the bacteria impacting their virulence. And finally, a new quantitative multiplex PCR analysis will be validated for diagnostic use, which will enable studying the levels of water moulds and relevant bacteria in fish and their surroundings in fish farms.


  • To study the occurrence of different genotypes of water mould strains in Finland and the differences in their virulence.
  • To explore the bacterial risk factors related to water mould infections in salmonid fish.
  • To develop a faster and more accurate method (multiplex PCR) for detecting water moulds and related bacteria.

These results enable the development of:

  • the assessment of disease pressure originating from the environment in fish farms 
  • control and treatment methods for the disease in fish farms

Key words:

Water moulds, Saprolegnia sp. genotyping, Iodobacter sp., Flavobacterium sp., PCR

Responsible project leader:

Viljamaa-Dirks Satu, Chief Specialist, Finnish Food Authority, Veterinary Bacteriology and Pathology Unit

Person at Finnish Food Authority responsible for the project:

Korkea-aho Tiina, Researcher, Veterinary Bacteriology and Pathology Unit

In cooperation with:

Åbo Akademi;
University of Jyväskylä

Project status:

In progress

Year of commencement:


Year of completion:


Project financed by: 

The European Union;
European Maritime and Fisheries Fund (EMFF);
ELY Centre





Page last updated 7/9/2019