Histopathological Evidence of Potential Pesticide-Associated Lesions in Wild Mammals of Nigeria

Abstract

Agricultural intensification and increased pesticide use pose growing risks to wildlife health, yet empirical evidence from tropical ecosystems remains limited. This study investigated histopathological alterations in wild mammals from Nigeria to assess tissue-level patterns consistent with environmental stressors in agricultural landscapes. A total of 141 tissue samples from eight mammalian species were examined using standard histological techniques. Overall, 56.7% of tissues exhibited pathological lesions, with significant variation among species (χ² = 22.262, df = 7, p = 0.002). Giant rats (Cricetomys gambianus) showed lesions in all examined tissues (100%), followed by grasscutters (Thryonomys swinderianus, 64.3%), porcupines, and Bushbuck (Tragelaphus scriptus) (66.7% each). Antelopes exhibited lower lesion occurrence (34.9%), while no lesions were detected in the single deer sample. Lesions were unevenly distributed across organs, with the liver most frequently affected (71.3%), followed by the lungs (12.5%) and kidneys (7.5%). Lesion occurrence was significantly associated with animal species (Cramer’s V = 0.397, p = 0.002), indicating species-specific susceptibility patterns likely influenced by ecological traits and physiological function. Although direct chemical residue analysis was not performed, the predominance of lesions in metabolically active organs suggests chronic exposure to environmental stressors common in pesticide-intensive agro-ecosystems. These findings highlight the potential value of small-bodied mammals as sentinel species and demonstrate the utility of histopathology as a sensitive, cost-effective biomarker for wildlife health assessment and ecological risk monitoring.