Haematological Effects of Sub-chronic Exposure to Cypermethrin in Wistar Rats

Cypermethrin is a synthetic pyrethroid insecticide widely used in Nigerian agriculture for pest control in crops, livestock ectoparasite management, and domestic vector control in many states including those in the North West and North Central zones. Concerns have arisen regarding its potential haematotoxic effects in non-target species following prolonged occupational or environmental exposure. This study evaluated the haematological effects of sub-chronic oral exposure to cypermethrin in Wistar rats over 28 days. Forty male rats were divided into four groups receiving 0, 10, 20, and 40 mg/kg cypermethrin by gavage daily. At the end of the exposure period, blood was collected for comprehensive haematological analysis including red blood cell count, packed cell volume, haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin concentration, white blood cell count, differential leucocyte count, and platelet count. Results showed a significant dose-dependent decrease in red blood cell count, PCV, and haemoglobin in groups receiving 20 and 40 mg/kg cypermethrin. Total white blood cell count was significantly elevated in the 40 mg/kg group, driven primarily by neutrophilia. Platelet counts were significantly reduced at the highest dose. Spleen weight was significantly increased in animals receiving 40 mg/kg, consistent with compensatory extramedullary haematopoiesis. These findings indicate that cypermethrin at high doses induces haematotoxicity in rats and underscore the need for safe handling practices and regulatory monitoring of pyrethroid use in Nigerian agriculture. Keywords: cypermethrin, haematotoxicity, pyrethroid, Wistar rats, sub-chronic.