Effectiveness of natural compounds against Gyrodactylus turnbulli parasites: Apex® Branchia

Arapi, Elissavet A., Isern-Subich, Maria Merce, Nuez-Ortín, Waldo G. and Cable, Joanne ORCID: https://orcid.org/0000-0002-8510-7055 2025. Effectiveness of natural compounds against Gyrodactylus turnbulli parasites: Apex® Branchia. Bulletin of the European Association of Fish Pathologists 10.48045/001c.145031

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Abstract

Despite continued growth in aquaculture, infectious diseases remain a critical concern causing annual losses of up to £10 billion. Many chemical treatments, widely used in the past, have now been banned due to their toxic effects on humans, fish and the environment. This sparked a shift towards natural compounds and herbal remedies that can reduce fish pathogens when incorporated in host diets. The challenge though is to find that ‘needle in the haystack’ - which of these compounds are most effective. Here, a reliable and consistent method was used that allows us to test the anti-parasitic activities of a botanical compound in multiple rounds, using the guppy-Gyrodactylus turnbulli system. Our blind feed trials confirm the efficacy of a commercially available product, Apex® (a mixture of organic acids, inactivated yeast and yeast extracts, herbal extracts and essential oils) significantly reduced parasite burden and increased host survival rate. Even though efficacy of natural compounds is both dose- and source-dependent, they can be adjusted according to host-parasite species and method of application. Additionally, feeding prior to parasite exposure likely enhances fish immune function, working synergistically with the direct effect that therapeutants have on the parasite. Concluding, Apex is a promising health-supporting natural functional feed additive, and botanicals can provide significant health benefits, urgently needed to protect the increasing global demand for suitable fish food.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Biosciences
Publisher:	European Association of Fish Pathologists
ISSN:	0108-0288
Date of First Compliant Deposit:	28 October 2025
Last Modified:	28 Oct 2025 12:00
URI:	https://orca.cardiff.ac.uk/id/eprint/181952

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