Many Stramenopile species belonging to the oomycetes (water molds) of the genus Saprolegnia infect fish and other aquatic vertebrates and invertebrates in aquaculture farms and natural habitats. Saprolegnia parasitica is one of the main causes of sapralegniasis disease, which is the second most economically important infection in aquaculture [1]. S. parasitica is responsible for up to 10% of salmonids mortality in fish farms however there is no effective way of treating saprolegniasis since the restriction of malachite green dye for its carcinogenic and teratogenic effect [1], [2]. For a long time, S. parasitica was thought to be an opportunistic pathogen that infects only immunosuppressed, wounded, or dead fish and cannot harm healthy salmonid embryos, however evidence of S. parasitica being a primary pathogen has recently emerged. Moreover, some researchers believe that S. parasitica is able to suppress immune response in fish [3].
The main objective of this work was to assess genotoxic and cytotoxic effects caused by S. parasitica to sea trout (Salmo trutta trutta) embryos erythrocytes using micronucleus and other nuclear abnormalities test. The results showed that S. parasitica causes genotoxic and cytotoxic lesions in the erythrocytes of S. trutta trutta embryos, indicating its pathogenicity.