Parasitic diseases, notably those caused by protozoan and monogenean ectoparasites such as Trichodina sp. and Gyrodactylus turnbulli, present significant challenges to aquaculture, impacting fish health, growth, and productivity. The confined conditions of aquaculture facilities exacerbate the spread and impact of these parasites, leading to increased morbidity, mo rtality, and reduced efficiency in fish cultivation. While traditional chemical treatments offer some effectiveness, their associated risks of toxicity and environmental damage highlight the need for investigating natural alternatives to manage parasitic infections . In our previous studies, we identified anti- parasitic effect of fatty acids and fatty acid ethyl esters (FAEEs), produced from the microalga Phaeodactylum tricornutum and its residue material
. To expand the potential application of FAEEs, we investigated the effect of a broad range of FAEEs against G. turnbulli and Trichodina sp. (protozoan) and proposed the potent natural sources for their preparation.
Methods: A ntiparasitic activity of FAEEs derived from fatty acids of various chain lengths and from natural sources, including: residue of P. tricornutum, coconut oil, and black soldier fly larvae (BSFL), was analyzed . Infection of G. turnbulli and Trichodina sp. in guppies and barramundi was examined, respectively. Analysis included in-situ antiparasitic testing, followed by fish toxicity assessment and in vivo efficacy i n the infected fish.
Results: FAEE prepared from P. tricornutum residue has effectively treated Trichodina sp. infection in barramundi. Of the most effective tested FAEEs, ethyl laurate (C12) was identified as a widely available not toxic and effective treatment candidate against both the tested parasites . Overall, FAEEs demonstrated potential as a sustainable and non-toxic alternative to traditional chemical treatments, effectively lowering infection prevalence in infected fish population.