Trans-stadial midgut development in Aedes aegypti L. (Diptera: Culicidae) is long-term impaired by sublethal concentrations of Schinus terebinthifolia Raddi (Anacardiaceae) leaf preparations.

Control of the vector Aedes aegypti L. is the main prophylactic measure for limiting the spread of dengue fever, chikungunya, and Zika virus diseases. In light of the environmental toxicity and resistance development associated with synthetic pesticides, plant-derived insecticides have been investigated as potential alternatives. A saline extract from Schinus terebinthifolia Raddi leaves and its fraction rich in cinnamic derivatives (designated F1) have been reported to be larvicidal against Ae. aegypti. This study evaluated the impacts of exposing third-instar Ae. aegypti larvae to sublethal concentrations of these preparations on trans-stadial midgut development. The larvae were incubated with the extract (0.6% w/v), F1 (0.2% w/v), or distilled water (control) for 24 h. After this period, they were transferred to distilled water and monitored until adult emergence. Larvae, pupae, and adults were collected, and their midguts were dissected and analyzed by optical and fluorescence microscopy. Treatment with the extract and F1 resulted in cellular deformation, hypertrophy, and vacuolization of the midgut epithelium across all life stages (larvae, pupae, and adults). The number of proliferative cells positive for phosphohistone H3 (PH3) was reduced by 73.6% in larvae and 72.7% in pupae treated with the extract or F1 compared with controls, indicating impaired midgut regeneration and remodeling. In contrast to the control group, proliferating cells were detected in adult midguts of individuals previously exposed to the extract. Caspase-3-positive apoptotic cells were observed in larvae and pupae exposed to the extract and F1, whereas no such cells were observed in controls. In conclusion, exposure of A. aegypti larvae to the saline extract and F1 chronically affected midgut development, leading to marked morphological alterations in subsequent life stages. These changes were associated with apoptosis and disruptions in cellular regeneration processes.