Evaluation of Moringa oleifera seed lectin in traps for the capture of Aedes aegypti eggs and adults under semi-field conditions

Abstract

The water-soluble lectin isolated from Moringa oleifera seeds (WSMoL) is a larvicidal, ovicidal, and oviposition-stimulating agent against Aedes aegypti under laboratory conditions. This study investigated the effect of WSMoL in traps for the capture of A. aegypti eggs and adult females under semi-field conditions and determined whether gravid females could detect WSMoL by an olfactory response. WSMoL was isolated according to a previously described procedure using chitin chromatography. The bioassays were performed in large cages (12.5 m(3)). Two traps for collection of eggs (ovitrap) or adult mosquitoes (MosquiTRAP(TM)) were placed in a cage. One was filled with WSMoL (0.1 mg/mL) and the other with tap water (negative control). An infusion of Panicum maximum leaves was used as a positive control. Forty gravid females were then released in each cage. After 2 (for oviposition) or 3 h (for female capture), the traps were removed, and the number of eggs or females was counted. An olfactometry assay was performed to investigate whether the effect of WSMoL on gravid females was linked to an olfactory response. WSMoL showed an oviposition-stimulating effect (65 ± 14%) that was similar (p < 0.05) to that promoted by the P. maximum infusion (67 ± 11%). The efficiency of MosquiTRAP(TM) in capturing gravid females was not increased by WSMoL. The olfactometry assay indicated that the response of females to WSMoL did not involve the stimulation of olfactory sensilla. WSMoL effectively captured eggs when used in ovitraps under semi-field conditions; this property, together with the ovicidal and larvicidal activities of this lectin, makes it an interesting candidate for A. aegypti control.