Water Added Probiotics Attenuates Sumithion‐Induced Toxicity on Growth, Intestinal Deformities, Erythrocytic Abnormalities, and Immunity in Nile Tilapia ( Oreochromis niloticus )

Probiotics are important microflora that help in improving gut health, enhancing immunity, and boosting overall well‐being. Sumithion (O, O‐Dimethyl O‐(3‐methyl 4‐nitrophenyl) phosphorothioate) is an organophosphate insecticide widely used in agriculture and aquaculture, has harmful effects in aquatic organisms due to its indiscriminate use. Therefore, this study evaluates the counteracting effects of multispecies probiotics ( Bacillus subtilis , B. thuringiensis Lactobacillus plantarum , and L. buchneri ) to sumithion toxicity in Nile tilapia ( Oreochromis niloticus ). Juvenile (12.84 ± 0.09 g) Nile tilapia were reared with four treatment groups: control, sumithion (0.3 mg/L), probiotics (1.0 mL/L), and sumithion + probiotics (0.3 mg/L + 1.0 mL/L) with three replicates for 42 days. Results showed that fish exposed to sumithion had significantly lowered weight gain (WG) and specific growth rate (SGR), while probiotics incorporation improved the growth performance. Probiotics mitigated sumithion‐induced effects by increasing hemoglobin (Hb) and decreasing glucose (Glu) levels, while also reducing the higher erythrocytic abnormalities. Sumithion exposure caused marked alterations in intestinal morphology, and these changes were partially restored by co‐administrations of multispecies probiotics, while enhanced intestinal mucosal folds, improving goblet and enterocytes cell numbers, and widen the lamina propria. Significantly higher and lower levels of mRNA for growth hormone (GH; gh ) and insulin‐like growth factors (IGFs; igf-1 and igf-2 ) genes were found in probiotics and sumithion‐exposed fish, respectively. Relative mRNA level for antioxidant genes (catalase [ CAT ] and superoxide dismutase [ SOD ]) was significantly increased in fish exposed to sumithion, while the nonsignificant differences was observed in probiotics and sumithion and probiotics treated fish. Conversely, the expression of immune‐related genes (tumor necrosis factor alpha [ TNF-α ], interleukin beta [ IL-1β ], and interferon gamma [ IFN-γ ]), was downregulated in sumithion‐treated fish, and relative mRNA levels increased following the addition of probiotics. Therefore, incorporating probiotics into the aquatic environment demonstrated beneficial effects on haemato‐biochemical properties, erythrocyte structure, and immune function, ultimately enhancing growth and countering the stress induced by sumithion pesticides.