TDK conference 2015

The research focuses on the water mold species causing the saprolegniosis of fish and their eggs and protection against them. The disease – first mentioned in the early 1920s – is caused by parasitic fungus of the Saprolegniaceae class. Saprolegnia species are a serious problem both in hatcheries and breeding farms. The pathogen settles indirectly, usually as a result of a primary cause, first on the surface of the body and then penetrating deeper into the tissue, interweaving organs with its hyphae. The growing fungus is visible to the naked eye, as the hyphae form cotton wool-like patches on the fish and the eggs. The treatment of the infection caused no problem until the Standing Committee on the Food Chain and Animal Health declared the treatment agent called malachite green oxalate a prohibited substance due to its carcinogen effects.

In this study I aimed to find out which disinfectant can effectively replace the malachite green. Besides effectiveness, economic criteria were also considered.

The in vitro experiments were conducted with three Saprolegnia species isolated from the hatchery, the Saprolegnia parasitica, the Saprolegnia ferax and the Saprolegnia australis. The treatment agent tests were carried out in an aqueous medium on hemp seeds interwoven with Saprolegniaceae fungi. Besides malachit green – which was used as positive control – copper oxychloride, bronopol, acriflavin, Divosan forte, chlorine dioxide, Betadine, peridox, azurina, boric acid and the aqueous solution of formaldehyde, formaline. These substances are all known for their antimicrobial impact, all of them are commercially available and can be used economically in industrial volumes.

The examination of the growth of samples placed on substrate showed that hyphae did not grow or were inhibited in growth and differentiation (conidiogenesis), compared to their control group treated with formalin, Divosan forte and Betadine.

We are preparing the in vivo phase of the research, during which the effective disinfectants will be tested on fertilized trout eggs in hatcheries.