The mitigating effect of dietary β-glucan against fipronil-induced intoxication in Nile Tilapia (Oreochromis niloticus): Histopathological, immunological, hematological, and biochemical analysis

Abstract

Background: Due to its remarkable effectiveness against a wide range of pests and insects at very low concentrations, the broad-spectrum fipronil pesticide is currently gaining popularity in the agricultural, public health, and international industries. However, the stressor effects of fipronil insecticides cause ecological disruption, growth retardation, immunosuppression, and higher fish mortality rates. Both animals and humans have demonstrated the effectiveness of prebiotics such as β-1,3-glucan in their diets. Aquaculture has recently increased in use because of its potential to control diseases, compete with environmental stresses, and promote fish growth.

Aim: The goal of this study was to determine how dietary β-1,3-glucan can protect Nile Tilapia (Oreochromis niloticus)fish from fipronil's harmful effects.

Methods: We randomly divided 240 fish into four equal groups. As a control, the first group (G1) was fed a standard diet. A 0.1% dose of -1, 3-glucan was added to G2. Fipronil was added to G3 at a concentration of 2.8 mg/l (1/10 96 h LC50). At the indicated concentrations, G4 was combined with β-1, 3-glucan, and fipronil. Alterations in vital signs, metabolic profiles, immunological responses, blood counts, and any histological abnormalities in the liver or spleen of the fish were investigated and recorded.

Results: The fipronil-exposed group exhibited slow mobility, respiratory discomfort, and increased mucus secretion. Several blood markers, like immunoglobulin M and lysozyme, were found to be significantly lower. On the other hand, the levels of aspartate aminotransferase, alanine aminotransferase, urea, creatinine, and cortisol in the serum were significantly higher. Liver histopathology revealed hemorrhagic blood vessels, steatosis in hepatocytes, hydropic degeneration, and widespread necrosis. Furthermore, we noted serious splenic parenchymal necrosis, hemorrhagic red pulp, white pulp depletion, and hemosiderosis. Histological changes were slowed by G4, which had β-1,3-glucan and fipronil. Moreover, it increases blood markers and physical activity levels.

Conclusion: The results show that β-1,3-glucan is an effective dietary supplement for Nile tilapia, and it improves their health, increases their immunity, and neutralizes fipronil contaminants in fish farming.

Keywords: Biochemical; Fipronil; Histopathological; Immunological; Nile Tilapia; Toxicity; β-1,3-glucan.

Fig. 1.. Showing the effect of fipronil and β-1,3-glucan on some hematological parameters; RBCs (red blood cells), total leucocytes counts, packed cell volume, hemoglobin for all experimental groups. According to Tukey’s Honestly test, the different letters (a–c) were significantly different between treatments at the p < 0.05 level.

Fig. 2.. Showing the effect of fipronil and β-1,3-glucan on some immunological parameters; lysozyme and immunoglobulin M for all experimental groups. According to Tukey’s Honestly test, the different letters (a–d) were significantly different between treatments at the p < 0.05 level.

Fig. 3.. Showing the effect of fipronil and β-1,3-glucan on some biochemical parameters; alanine aminotransferase and aspartate aminotransferase as liver function markers, urea and creatinine as kidney function markers, and cortisol for all experimental groups. According to Tukey’s Honestly test, the different letters (a–c) were significantly different between treatments at the p < 0.05 level.

Fig. 4.. (a, b): Section of Nile Tilapia (Oreochromis niloticus) liver of the G1; control and G2 supplemented with β-glucan. a) showing normal, homogenous, intact hepatic parenchyma with normal central vein. b) Higher magnification of figure a showing normal and distinct radiated hepatic cords from the central vein to the periphery of the hepatic lobules (long arrow) with normal hepatocytes of irregular polygonal shaped cells with single, central, large vesicular nucleus and pale cytoplasm with slightly vacuolations (single arrow head), large like kupffer cells (short arrow) and melanomacrophage centers (double arrow heads).(c–k): Liver of fish of the G3 exposed to fipronil, c) showing diffuse necrosis, hydropic degenerations and vacuolations within the hepatocytes with disorganization of the hepatic cords (arrow head). d) showing diffuse microvesicular fatty degenerations , pyknotic central nuclei and pale cytoplasm with sever vacuolations (arrow), beside diffuse area of hydropic degeneration (arrow head). e) showing sever coagulative necrosis with homogeneous and acidophilic cytoplasm, due to the coagulation of cytoplasmic proteins (arrow head) and diffuse microvesicular fatty degenerations (arrow). f) showing sever congestion and hemorrhage of the central vein (arrow). g) showing congestion, hemorrhage and extravasated erythrocytes in between the hepatocytes (arrow). h, i) showing sever congestion and hemorrhage in the portal blood vessels. j) showing sever necrosis of hepatocytes infiltrated with numerous lymphocytes (arrow head). k) showing sever thickening of the bile duct with fibrous tissue proliferation (arrow head).(l): liver of fish of the G4 supplemented with 1,3 β-glucan and fipronil showing normal, intact hepatic parenchyma and hepatic cord, but with mild to moderate congestion within the central vein (arrow). Stain: All (hematoxylin and eosin). Magnification power: All = X 400, except for a, f = X 100, and i = X 40.

Fig. 5.. (a) Section of Nile Tilapia (Oreochromis niloticus) G1 spleen; control group showing normal, intact splenic parenchyma; white pulp (arrow heads) and red pulp (arrow).(b) Section of Nile Tilapia (O. niloticus) G2 spleen supplemented with β-glucan showing normal, intact splenic parenchyma; white pulp (arrow heads) and red pulp (arrow).(c–f) Section of Nile Tilapia spleen of the G3 exposed to fipronil, c) showing necrosis of the splenic parenchyma; white and red pulps with some loss of normal architecture and depletion of the white pulp (arrow head). d, e) showing severe hemorrhage; hemolysis of RBCs and escape of large amount of haemosidrin pigment that accumulated forming large golden yellow patches of haemosiderin pigments within the splenic parenchyma (arrow). f) showing severe congestion and hemorrhage within the splenic blood vessels; red pulp (arrow).(g) Section of Nile Tilapia spleen of the G4 supplemented with 1,3 β-glucan and fipronil showing normal, intact splenic parenchyma but with mild depletion of white pulp (arrow head) and mild haemosidriosis represented in small golden yellow patches of haemosiderin pigments within the splenic parenchyma (arrow). Stain: All (hematoxylin and eosin). Magnification power: All = X 100, except for a and b = X 40.