Effects of Achyranthes aspera Extracts on the Survival and Midgut Histo-architecture of Aedes aegypti L. Early IV Instars

Abstract

Aedes aegypti L.; one of the most important insect vectors in the world; transmits several diseases of concern; Zika, yellow fever, Chikungunya, dengue and dengue haemorrhagic fever. Despite multifarious problems on humans, non-targets and environment; caused by synthetic chemical insecticides; these are still the prime and preferred control measures against dengue vector. Alternative control strategies using eco-friendly and bio-degradable plant products are being explored. The present study investigates the toxic potential of the hexane extract of the leaf and stem of Achyranthes aspera against Ae. aegypti. The larvicidal potential of extracts was evaluated against dengue larvae as per WHO protocol. Subsequent concentration and time-dependent studies assessed their effects on the larval midgut histo-architecture using microtomy techniques. Larvicidal bioassays with A. aspera extracts revealed their appreciable larvicidal potential. Hexane extract of the leaf resulted in respective LC30, LC50 and LC90 values of 67, 83 and 140 ppm while exposure to hexane extract of the stem showed respective values of 55, 68 and 115 ppm. Extract-exposed larvae at various lethal levels exhibited significant damage, shrinkage, distortion and vacuolization of gut tissues and peritrophic membrane. The disintegration of epithelial cells and cytoplasmic organelles evidenced stomach poison potential of the extracts. The extent of toxicity and damage was concentration and time-dependent; the stem extract imparted more deleterious effects as compared to the leaf extract. Present findings suggest the utilization of A. aspera as an alternate control strategy against Ae. aegypti; though further studies against non-targets are needed to ascertain its use in the fields.