Fish Parasites in Aquaculture: can we control them all?

Trabajo presentado en el 15th International Conference of Parasitology, celebrado en Copenhague (Dinamarca) del 21 al 26 de agosto de 2022.Parasites are a major and recurrent problem in aquaculture, with heavy economic impact. These costs include those due to mortality, morbidity, poor growth, reduction of feed efficiency, parasitic castration, treatments and biosecurity measures, mort disposal, etc. A brief overview of the main fish parasites affecting marine aquaculture, with emphasis on sea cage farming in Europe will be presented. To understand the current situation some reflections will be provided about what should be done to set-up efficient means of control in order to hold parasites in a sustainable way. Aquaculture production often occurs in open or semi-open systems, where the level of containment and biosecurity applicable could never reach what is feasible in terrestrial farming. Sea cages pose a challenge for parasite control: 1) water cannot be controlled; 2) biofouling in nets and ropes favours entangling of some stages and the live of invertebrates that can be intermediate hosts; 3) juveniles are stocked sometimes from distant areas, bringing with them exotic parasites; 4) surrounding wild fish can be natural or reservoir hosts; and 5) non-controlled effluents (mucus casts, faeces, dead animals, escapees) allow parasite life cycles keep going. Sustainable control has to be based on three major pillars: 1) deep knowledge of the parasite, this means to know its life cycle, to achieve its in vitro culture, to develop an in vivo experimental infection, and to decipher all its biological weapons; 2) knowledge of the environment, including farm management, water conditions and diets; and 3) knowledge of the host, including the host-parasite interaction and the immune response, which will allow to introduce immunomodulatory measures and future vaccines. Funding: ParaFishControl H2020 EU project (634429)