Poikilocytosis and tissue damage as negative impacts of tramadol on juvenile of Tilapia (Oreochromis niloticus).

Pharmaceuticals residue was detected in the water bodies as a consequence of the incomplete treatment. Recently, the side impacts of that residue on aquatic creatures have received a considerable attention. However, there is insufficient information about the effect of the most consumed narcotic drug (tramadol) on fish as an aquatic model. Thus, this study aims at investigating the poikilocytosis and tissue damage in Oreochromis niloticus after the exposure to 100 and 200 mg/L of tramadol hydrochloride. Three groups of fish were used; one as a control group, and the other two groups were exposed to 100 mg/L and 200 mg/L of tramadol hydrochloride respectively for 25 days. Exposure to tramadol caused a significant increase in the percentage of poikilocytosis compared to the control group. Poikilocytosis included tear-drop cell, spindle-shaped cell, sickle cell, schistocyte, blebbed cell, acanthocyte, eccentric nucleus, amoebocyte, dividing cell, and crenated cell. Moreover, liver tissue in fish exposed to tramadol showed degeneration and vacuolization of hepatocytes and atrophy of pancreatic acini as signs of histopathological alterations. Histopathological changes of brain showed severe gliosis, dark neurons, and vacuolization in fish exposed to tramadol compared to control fish. Gills tissue showed erosion, epithelial lifting, and secondary lamellae shrinking in fish exposed to tramadol compared to control fish. In conclusion, tramadol induced histopathological changes in liver, brain, and gills of Oreochromis niloticus as well as poikilocytosis were indicated clearly. Therefore, tramadol leakage to waters should be avoided to preserve aquatic creatures.