Toxicity of Two Therapeutants Hydrogen Peroxide and Formalin in Nile Tilapia (Oreochromis niloticus)

The FDA has granted approval for the use of chemicals hydrogen peroxide and formalin in aquaculture. The toxicity of these two compounds was evaluated in the current study for freshwater Nile tilapia (Oreochromis niloticus) weighing 75 ± 2.5g. For 96 hours, ten fish each were subjected in triplicate to concentrations of hydrogen peroxide at 0 ppm, 150 ppm, 250 ppm, 350 ppm, 450 ppm, and 600 ppm. Similarly, for 96 hours, 10 fish each were subjected in triplicate to the following concentrations of formalin: 0 ppm, 50 ppm, 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, and 450 ppm. Every day, the mortality rate was noted. Each chemical's LD50 was determined using the non-linear regression approach. Hematological parameters, such as white blood cells, red blood cell, hemoglobin, and thrombocyte number as well as serum parameters, such as ALT, AST, creatinine, and BUN, and enzymes that inhibit free radicals, such as SOD, CAT, and GSH, were determined following the collection of blood and liver tissue. Following the slaughter fish. The liver, muscle, gills, and heart were collected for histopathology. The LC50 values for formalin and hydrogen peroxide were found to be 231.2 µg/ml and 314.6 µg/ml, respectively. Sublethal concentrations of hydrogen peroxide significantly increased hematological parameters such as total WBC, RBC, hemoglobin, and thrombocyte count, and serum parameters such as ALT, AST, creatinine, and BUN, while antioxidant enzymes such as SOD, CAT, and GSH significantly decreased. Fish exposed to formalin had significantly higher levels of ALT, AST, creatinine, BUN, and significantly lower levels of antioxidant enzymes. Histology of the muscles of fish that were exposed to sublethal concentrations of two chemicals showed hyperplasia, lamellar fusion of the gills, infiltration of hemocytes and muscular atypia in the heart, and separation of muscle fiber bundles in the liver.