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Challenges and Perspectives in Parasite Control in European Marine Aquaculture

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By Milthon Lujan

In Europe, marine aquaculture, particularly in the Mediterranean region, has witnessed significant growth in recent decades in terms of production volumes. However, this flourishing industry is not without its challenges, with one of the most pressing being parasitic infections in farmed fish. These infections can occasionally be severe and result in considerable economic losses.

A study published by scientists from the Hellenic Centre for Marine Research, the Universitat Autònoma de Barcelona, the University of Thessaly, and Skretting Aquaculture Innovation conducted a review that assessed the knowledge of using medications for controlling parasitic diseases in European fish farming, with a particular focus on fish mariculture in the Mediterranean.

The Problem of Parasitic Infections in European Aquaculture

Parasitic infections pose a persistent threat to aquaculture in Europe, especially in the Mediterranean region. These parasites can significantly impact the health of farmed fish, reduce their growth and quality, and ultimately lead to substantial economic losses for producers.

The study reports that the primary ectoparasites include the monogenean Sparicotyle chrysophrii in gilthead seabream, Diplectanum aequans in European seabass, and Sciaenicotyle panceri in meagre, along with copepods and isopods like Lernanthropus kroyeri and Ceratothoa oestroides in European seabass. Additionally, endoparasites such as Enteromyxum leei and Enterospora nucleophila affect the digestive system of sparids.

Legislation for Parasitic Disease Treatment

In Europe, particularly in the European Union (EU), most registered antiparasitic drugs were initially applied to combat sea lice infections in Atlantic salmon, and these drugs were eventually authorized for other non-salmon producing countries.

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However, the study highlights that in the Mediterranean, sea lice are not a problem, but other copepods like Lernanthropus kroyeri can cause severe issues in European seabass.

Lack of Commercial Vaccines

Unlike some bacterial and viral diseases, there are no commercially available vaccines for most parasites affecting farmed fish. In most cases, due to the lack of vaccines, controlling parasitic infections relies primarily on chemicals. In other cases, however, the possibility of controlling parasitic infections at the farm level is much more complicated due to the complexity of parasite life cycles.

Therapeutic Strategies for Parasite Control

Bath Treatments

Therapy against parasites in European aquaculture, particularly in the Mediterranean region, traditionally relies on chemical baths. Compounds such as formalin and, to a lesser extent, hydrogen peroxide are used in these baths. While these baths can be effective, they also pose challenges related to their environmental impact and the need for withdrawal periods to ensure food safety.

Oral Treatments

Therapeutic antiparasitic treatment via diet offers specific advantages over bath treatments in certain cases. Unlike bath treatments, oral therapy in cages is simple, fast, cost-effective, and weather-independent.

Environmental Concerns

Aquaculture activities without proper control and monitoring can have significant impacts on the surrounding environment. Among these practices, the discharge of antiparasitic products is one of the most environmentally hazardous.

The effects of antiparasitic chemicals can vary depending on various factors such as the quantity of the substance, the discharge of water used during treatment, and the type of affected environment. However, the environmental effects of any chemical primarily depend on the specific chemical characteristics of the substance used, which can affect its solubility in water, biodegradation, and persistence in the environment.

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Integrated Pest Management Strategies

Furthermore, the implementation of integrated pest management strategies, involving various management practices with limited chemical use, should be prioritized. These strategies will not only reduce dependence on chemical baths but also contribute to the long-term sustainability of aquaculture.

Conclusions

Parasitic infections pose a constant challenge to European marine aquaculture, with the Mediterranean region being a critical focal point. As the industry progresses, it is essential to address these challenges effectively and sustainably. This entails seeking safer and environmentally friendly therapies like dietary antiparasitics and implementing integrated pest management strategies.

“In conclusion, available antiparasitics will always be considered an important tool in reducing the impact of parasitic diseases in Mediterranean fish farming. However, they cannot be seen as the sole solution for parasitic diseases due to concerns related to applicability, legal aspects, consumer health, and environmental impact,” the researchers concluded.

The information provided in this scientific review should serve as a guide for future research and promote effective and prudent parasite control practices in farmed fish aquaculture in the Mediterranean and beyond. The pursuit of innovative and sustainable solutions is crucial to ensuring the continued success of aquaculture in Europe and global food security.

The study has been funded under the Cure4Aqua project, which is supported by Horizon Europe, the European Union’s research and innovation program.

Contact
George Rigos
Institute of Marine Biology, Biotechnology, and Aquaculture
Hellenic Centre for Marine Research
46.7 Athinon – Souniou ave, 19013 Anavissos
Attiki, Greece.
Email: grigos@hcmr.gr

Referencia (open access)
Rigos, G, Padrós, F, Golomazou, E, Zarza, C. Antiparasitic approaches and strategies in European aquaculture, with emphasis on Mediterranean marine finfish farming: Present scenarios and future visions. Rev Aquac. 2023; 1-22. doi:10.1111/raq.12857

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