Inhibition of acetylcholinesterase and histopathological changes in Aedes aegypti and Aedes albopictus larvae exposed to ethanolic extract of Acmella oleracea (L.) R.K. Jansen (Asteraceae)

Important arboviruses for public health such as Dengue, Zika, and Chikungunya are transmitted by mosquito vectors, primarily Aedes aegypti and Aedes albopictus. The control of populations of these mosquitoes can be carried out by mechanical, chemical, and biological control. In view of the environmental impacts caused by synthetic chemical insecticides, the search for botanical larvicides with larvicidal potential has intensified. The objective of this work is to investigate the occurrence of acetylcholinesterase inhibition and histopathological alterations in Aedes aegypti and Aedes albopictus submitted to treatment with the ethanolic extract of the leaves of Acmella oleracea as possible mechanisms of larvicidal action. Larvae of Aedes aegypti and Aedes albopictus were exposed to treatment with the ethanolic extract of Acmella oleracea for an exposure period of 24 hours. After this time, larval mortality was recorded, and the larvae were separated in order to investigate the mechanisms of action. The ethanolic extract of Acmella oleracea had an LC50 of 29.15 µg.mL-1 and 16.00 µg.mL-1 against Aedes aegypti and Aedes albopictus, respectively. Significant reductions in acetylcholinesterase activity were observed in larvae treated with the ethanolic extract of Acmella oleracea, as well as histopathological changes in the midgut of treated larvae, including loss of integrity of the intestinal epithelium, vacuolation of the cell cytoplasm, and disruption of the peritrophic matrix. These results suggest that that the mechanism of action of the ethanolic extract of Acmella oleracea against Aedes larvae includes the potential to inhibit acetylcholinesterase and cause histopathological alterations in the midgut.