Immunomodulatory and histopathological effects of dietary lauric and benzoic acids on deltamethrin-induced mucosal immune disruptions in Nile tilapia (Oreochromis niloticus).

Deltamethrin (DLM), a pyrethroid insecticide and common aquatic contaminant, impairs immunity in Nile tilapia (Oreochromis niloticus). This study evaluated the protective effects of lauric acid (LA) and benzoic acid (BA), both individually and in combination, against DLM-induced mucosal injury and immunosuppression. One hundred fifty juvenile Nile tilapia were distributed into five groups: a negative control, a positive control (DLM group) for 60 days, and three groups pre-fed with either 1 g/kg lauric acid, 1 g/kg benzoic acid, or their combination for 30 days prior to a subsequent 30-day DLM challenge. The evaluation included histopathological examination of intestinal and gill tissues, alongside assessment of immune markers, including IgM levels and lysozyme activity, serum triglyceride levels, and IL-1β gene expression. Results indicated that DLM exposure caused severe mucosal damage, characterized by necrotic enteritis and gill epithelium desquamation, concurrent with a significant suppression of immune markers and lipid metabolic disruption. However, supplementation with LA and BA, both individually and in combination, significantly ameliorated these toxic effects. Notably, the combined treatment (LA + BA) enhanced protective efficacy, resulting in the most pronounced restoration of mucosal barrier integrity, normalization of serum triglycerides, IL-1β upregulation likely reflects restoration of immune responsiveness following DLM-induced suppression rather than generalized pro-inflammatory activation, and a significant elevation in immune parameters compared to individual treatments. These findings suggest that lauric and benzoic acids represent a promising strategy to mitigate DLM-induced immune toxicity in Nile tilapia. Consequently, the dietary administration of organic acids may provide immunomodulatory activity, reducing mucosal damage and mitigating DLM-induced toxicity.