Plant- and Bacteria-Derived Compounds with Anti-Philasterides dicentrarchi Activity

Area of Science:

• Aquaculture
• Parasitology
• Marine Biology

Background:

• Scuticociliatosis, caused by *Philasterides dicentrarchi*, leads to significant losses in farmed fish.
• Current vaccines are serotype-specific, necessitating alternative disease prevention strategies.
• Many chemical treatments are toxic to aquatic life, limiting their use in disease management.

Purpose of the Study:

• To identify natural compounds with anti-parasitic activity against *P. dicentrarchi*.
• To evaluate the toxicity of these compounds to fish cell lines.
• To assess the potential of safe, natural compounds for reducing parasite loads in aquaculture settings.

Main Methods:

• Exposure of *P. dicentrarchi* to various concentrations of natural compounds.
• Determination of ciliate mortality rates at different incubation times.
• Assessment of compound toxicity using the EPC cell line.

Main Results:

• Tomatine, plumbagin, and 2',4'-dihydroxychalcone demonstrated significant anti-ciliate activity in a dose-dependent manner.
• 2',4'-dihydroxychalcone exhibited the lowest toxicity to EPC cells, inhibiting 50% of parasite growth at 7.54 μM with minimal cell death.
• *Pseudomonas* H6 surfactant (PS) was toxic to *P. dicentrarchi* with reduced toxicity to EPC cells (LC50 for ciliate at 7.8 μg/mL resulted in 14.9% EPC cell death).

Conclusions:

• 2',4'-dihydroxychalcone and *Pseudomonas* H6 surfactant show promise for reducing *P. dicentrarchi* in seawater.
• These compounds could mitigate the risk of scuticociliatosis in farmed fish populations.
• Further research into these natural compounds may lead to safer, more effective aquaculture disease control methods.