Effect of a Mixed Herb—Enriched Diet on the Innate Immune Response and Disease Resistance of Paralichthys olivaceus against Philasterides dicentrarchi Infection

We investigated the effect of a mixed herb—enriched diet obtained from pomegranate Punica granatum , Dalmatian chrysanthemum Chrysanthemum cinerariaefolium , and mastic‐leaved prickly‐ash Zanthoxylum schinifolium on innate immune mechanisms (e.g., phagocytosis activity, respiratory burst activity, alternative complement activity, lysozyme activity, and disease resistance) of olive flounder Paralichthys olivaceus against the scuticociliate Philasterides dicentrarchi . All experimental groups were challenged with P. dicentrarchi (1 × 10 5 ciliates/mL) through intraperitoneal administration of the pathogen (50 μL) on day 1. On day 7, the infected groups were fed 0, 5, 50, and 100 mg/kg of the enriched diets. The innate immune parameters, cumulative mortality, and relative percent survival (RPS) were assessed at weeks 1, 2, 3, and 4. Administration of 50 or 100 mg/kg of the herbal‐enriched diet enhanced immunity throughout the experimental period. However, at the 5‐mg/kg dosage, the enriched diet did not enhance the innate immune estimates at any time. At doses of 50 and 100 mg/kg, administration of the diet preceding the challenge with P. dicentrarchi decreased the percentage cumulative mortality in the experimental groups and thereby increased RPS values. This study reports that administration of 50 or 100 mg/kg mixed herbal—enriched diet could positively influence the innate immune response to P. dicentrarchi and enhance the health status of olive flounder with respect to this microbe.