Haematological and Biochemical Effects of Long-Term Organophosphate Use in Sheep in Plateau State, North Central Nigeria

Organophosphate compounds are extensively used for ectoparasite control in sheep in north-central Nigeria, yet the cumulative haematological and biochemical effects of chronic exposure in smallholder flock settings are not well characterised. This study evaluated the haematological and biochemical effects of long-term organophosphate use in Yankasa sheep at farms in Plateau State, North Central Nigeria. Sixty sheep were divided into two groups based on organophosphate dipping frequency: a high-exposure group dipped monthly for more than two years and a low-exposure group dipped once every four months for less than one year. Complete blood count and serum biochemical analysis including cholinesterase activity, hepatic enzymes, creatinine, and antioxidant markers were performed. High-exposure sheep showed significantly reduced serum butyrylcholinesterase activity, indicative of organophosphate-mediated enzyme inhibition, alongside significantly elevated aspartate aminotransferase and alkaline phosphatase values. Haemoglobin and packed cell volume were modestly reduced in the high-exposure group. Malondialdehyde was elevated and superoxide dismutase reduced in the high-exposure sheep, indicating oxidative stress. Erythrocyte morphological abnormalities including acanthocytes were noted on blood films from high-exposure animals. These findings indicate cumulative subclinical organophosphate toxicity in chronically exposed sheep and strongly support the implementation of farmer education programmes on safe organophosphate use and rotation with non-organophosphate ectoparasiticides in Plateau State. Keywords: organophosphate, cholinesterase, chronic toxicity, sheep, haematology.