Effect of Curcuma longa rhizome extract and curcumin against laboratory-reared Aedes Aegypti (Diptera: Culicidae) larvae: Alterations of cell ultrastructure and immunoreactivity of octopamine and tyramine in the midgut

Abstract

Plant bioactive compounds, as an alternative insecticide, play an essential role in mosquito control. The purpose of this study was to evaluate the effect of Curcuma longa rhizome extract and curcumin against Aedes aegypti larvae, focusing on changes in the cell ultrastructure and immunoreactivity of octopamine (OA) and tyramine (TA) in the midgut. The larval bioassay was used following WHO protocols. Ae. Aegypti 3rd – 4th instars larvae collected from the laboratory were exposed to both different concentrations of C. longa rhizome extract and curcumin. Ultrastructural changes in the midgut cells were tested by transmission electron microscope (TEM). OA and TA in the midgut were detected by the immunohistochemical method. At 24 h, curcumin killed 100% of Ae. Aegypti larvae at a concentration of 4 ppm. The LC50 values of curcumin and the rhizome extract were 1.522 and 4.074 ppm respectively. The curcumin caused ultrastructural changes in the larval midgut; damaged cells, epithelial cells microvilli, cell membranes, nucleus, mitochondria, and other cell organelles. Curcumin and the rhizome extract decreased the immunoreactivity of OA and TA in the larval midgut. Curcumin showed significant larvicidal activity against Ae. aegypti larvae mediated by damaged cells and decreased immunoreactivity of OA and TA in the midgut.