Dietary Sweet Basil and Thyme Essential Oils Boost Nile Tilapia Growth and Immunity Against Aeromonas hydrophila

Intensive aquaculture of Nile tilapia faces significant challenges from infectious diseases like motile aeromonad septicemia, caused by Aeromonas hydrophila. Current reliance on antibiotics raises concerns about resistance and environmental impact, driving the search for sustainable alternatives. Immunostimulants, particularly herbal supplements, offer a promising strategy to enhance fish health and disease resistance by bolstering innate immune responses and modulating cytokine profiles, thereby reducing susceptibility to pathogens and improving overall productivity.

Researchers fed 180 juvenile Nile tilapia (13.21 ± 0.16 g) for 60 days with one of three diets: a control diet, a diet supplemented with 1% Ocimum basilicum essential oil, or a diet with 0.5% Thymus vulgaris essential oil. Fish were housed in three replicates of 20 per treatment. Following the feeding period, fish were challenged via intraperitoneal injection with 0.1 mL of 1.5 × 10^8 CFU mL⁻¹ Aeromonas hydrophila. Growth, hematological, serum biochemical, and innate immune parameters (lysozyme, nitric oxide, phagocytic index) were measured at days 30, 60, and 75 (15 days post-challenge). Cytokine concentrations (TNF-α, IL-1β, IL-6, IL-2, IL-10) and differential leukocyte counts were assessed at day 75, alongside histopathological analysis of hepatic and cephalic kidney tissues.

Both Ocimum basilicum and Thymus vulgaris essential oil supplements significantly enhanced several key health indicators in Nile tilapia. > Growth performance, including final body weight and weight gain, was significantly improved in supplemented groups compared to controls (P ≤ 0.05). Hematological indices also saw significant improvements, with increased hemoglobin concentration and higher erythrocyte and total leukocyte counts (P ≤ 0.05). Serum protein profiles, including total protein, albumin, and globulin levels, were elevated in the essential oil groups (P ≤ 0.05), indicating improved nutritional status and immune function. Furthermore, innate immune function was robustly boosted, evidenced by significantly higher lysozyme activity, nitric oxide production, and phagocytic index in treated fish compared to the control group (P ≤ 0.05). The abstract specifically noted that the diet supplemented with 1% O. basilicum essential oil produced substantial resistance, although specific survival rates or further details were not provided in the truncated abstract. These findings collectively demonstrate a potent immunomodulatory and growth-promoting effect of these essential oils.