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Aquaculture: Environmental‐friendly treatment for fish diseases

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By Milthon Lujan

By Angelina Tittmann*
Germany – Velvet disease is a dreaded ailment. This infection is caused by dinoflagellates of the genera Amyloodinium and Piscinoodinium, and affects freshwater and marine ornamental and food fish. In aquariums and aquaculture, the disease invariably causes considerable mortality, and thus financial losses. In her PhD thesis, Thora Lieke combined the risks and benefits of current treatment options and new approaches. Her article has been acknowledged as a top downloaded paper.

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When fish develop a velvet covering, this should be seen as an alarm signal. In many cases, they have velvet disease, a highly infectious parasitic disease that is fatal if left untreated. Therapeutants containing copper, malachite green or methylene blue were traditionally available. However, their residues are discharged into the environment, and are highly toxic to other organisms. As a result, these chemicals have been banned for use in aquaculture in several European countries; a prohibition for commercial ornamental fishkeeping is expected to follow.

This has led to an intensive search for alternative treatment options, also to combat other pathogens. In Reviews in Aquaculture, Thora Lieke and her colleagues provide an overview of traditional and new therapeutants for the treatment of various parasitic diseases. In the search for environmentally friendly treatments for fish diseases, they recommend concentrating on two aspects: treating parasites using residue‐free or naturally occurring substances; and enhancing the immune system of fish.

These residue-free, “alternative” therapeutants include hydrogen peroxide and peracetic acid, which have been proven to be effective against a variety of aquatic pathogens, also in the treatment of velvet disease. However, they may add to the stress level of the infected fish. The use of natural feed supplements such as vitamins, plant extracts, prebiotics and probiotics is therefore being investigated in numerous studies. These supplements activate the immune system and increase animal welfare, making fish less vulnerable to diseases. Humic substances are also known to act as immunostimulants, and are the subject of research throughout the world. As a natural part of aquatic ecosystems, they can be ingested via the gills, as proven by Thora Lieke and her colleagues in another study.

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Contact person
Thora Lieke
Scientific Staff
Research group
Fish Pathology, Ecotoxicology and Stress Ecology

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Thomas Meinelt
Research Group Leader
Research group
Fish Pathology, Ecotoxicology and Stress Ecology

Reference (open access):
Thora Lieke; Thomas Meinelt; Seyed Hossein Hoseinifar; Bo Pan; David L. Straus; Christian E. W. Steinberg. 2020. Sustainable aquaculture requires environmental-friendly treatment strategies for fish diseases. Reviews in Aquaculture. – 12(2020)2, S. 943-965 http://dx.doi.org/10.1111/raq.12365 

Thora Lieke; Christian E. W. Steinberg; Bo Pan; Irina V. Perminova; Thomas Meinelt; Klaus Knopf; Werner Kloas. 2021. Phenol-rich fulvic acid as a water additive enhances growth, reduces stress, and stimulates the immune system of fish in aquaculture. Scientific Reports. – 11(2021), art. 174. 

Source: IGB

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