Effect of medicinal plants on the mosquito vectors from the different agro-climatic regions of Tamil Nadu

ABSTRACT Vector control plays a key role in prevention and control of major vector-borne infectious diseases in tropical and subtropical regions. The three main climatic factors that affect malaria transmission and distribution are temperature, precipitation and relative humidity. Aedes aegypti, commonly known as the Yellow Fever Mosquito, is a mosquito that can host the dengue fever, Chikungunya and yellow fever viruses. Medically most important species, Culex quinquefasciatus, breeds in waters polluted with organic debris such as rooting vegetation, household refuse and excreta. Chemical control use of pesticides is still the most important element in the integrated approach to vector control. But they are non-selective and harmful to other beneficial organisms. Hence, botanical have grown very important in controlling the mosquito vectors. Laboratory and field investigations have been made to evaluate the combined effect Clerodendron inerme, Acanthus ilicifolius on three species of mosquito vectors, Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. Different concentrations of Clerodendron inerme and Acanthus ilicifolius have been tested on the various stages of species of mosquito vectors. Lethal concentrations (LC 50 and LC 90 ) were also worked for the different larval stages of mosquitoes. Significant increased mortality was evident after the plant extracts. The lethal effect on mosquito larvae may be due to the active plant compounds on the gut lining of the mosquito larvae. The larval density was decreased after the treatment of plant extracts at the breeding sites (drinking water and ditches water), and hence, these plant extracts of the suitable alternatives of synthetic insecticides for the mosquito vector management

Mosquito larvicidal properties of Orthosiphon thymiflorus (Roth) Sleesen. (Family: Labiatae) against mosquito vectors, Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti (Diptera: Culicidae)

AbstractObjectiveTo determine the mosquito larvicidal activities of hexane, chloroform, ethyl acetate, acetone and methanol leaf extract of Orthosiphon thymiflorus (O. thymiflorus) against Anopheles stephensi (An. stephensi), Culex quinquefasciatus (Cx. quinquefasciatus) and Aedes aegypti (Ae. aegypti).MethodsThe larvicidal activity was assayed against three mosquito species at various concentrations ranging from (50-450 ppm) under the laboratory conditions. The LC50 and LC90 value of the O. thymiflorus leaf extract was determined by Probit analysis.ResultsThe LC50 values of hexane, chloroform, ethyl acetate, acetone and methanol extract of O. thymiflorus third instar larvae of An. stephensi were LC50= 201.39, 178.76, 158.06, 139.22 and 118.74 ppm; Cx. quinquefasciatus were LC50=228.13, 209.72, 183.35, 163.55 and 149.96 ppm and Ae. aegypti were LC50=215.65, 197.91, 175.05, 154.80 and 137.26 ppm, respectively. Maximum larvicidal activity was observed in the methanolic extract followed by acetone, ethyl acetate chloroform and hexane extract. The larval mortality was observed after 24 h exposure. No mortality was observed in control.ConclusionsThe present results suggest that the effective plant crude extracts have potential to be used as an ideal eco-friendly approach for the control of mosquito vectors. This study provides the first report on the larvicidal activity of this plant crude solvent extract of against An. stephensi, Cx. quinquefasciatus and Ae. aegypti mosquitoes

Larvicidal and pupicidal activity of synthesized silver nanoparticles using Leucas aspera leaf extract against mosquito vectors, Aedes aegypti and Anopheles stephensi

Mosquitoes are one of the most medically significant groups of vectors, having an ability to transmit parasites and pathogens that can have devastating impacts on humans. The development of reliable and ecofriendly processes for the synthesis of metallic nanoparticles is an important step in the field of application of nanotechnology. In this study, we address the biosynthesis of silver nanoparticles (AgNPs) using Leucas aspera leaf extract, and evaluate its lethal concentration (LC50 and LC90) values against first to fourth instar larvae and pupae of the mosquito vectors, Aedes aegypti and Anopheles stephensi. The nanoparticles were characterized by UV-Vis spectrum, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transformed infrared spectroscopy analysis. Larvae and pupae were exposed to varying concentrations of aqueous extracts of synthesized AgNPs for 24 h. The maximum mortality was observed from synthesized AgNPs, with LC50 values for I-IV instars and pupae ranging from 13.06 to 25.54, and LC90 values ranging from 24.11 to 47.34 for A. aegypti; for A. stephensi, the corresponding LC50 values ranged from 12.45 to 22.26, and the LC90 values ranged from 23.50 to 42.95. With methanol leaf extract of L. aspera against A. aegypti, the LC50 values ranged from 174.89 to 462.96 and the LC90 values ranged from 488.16 to 963.74; for A. stephensi, the corresponding LC50 values ranged from 148.93 to 417.07 and the LC90 values ranged from 449.72 to 912.94. The study suggests that nanoparticles could be a preferred alternative to the most hazardous existing chemical pesticides, contributing to a more healthy environment by providing an ideal ecological and user-friendly vector control strategy for managing malaria and dengue, and contributing to their eventual elimination in the near future

Larvicidal activity of indigenous plant extracts on the rural malarial vector, Anopheles culicifacies Giles. (Diptera: Culicidae)

Vector control is one of the most important components in combating vector-borne diseases throughout the world. Application of insecticides is a widely known and popular vector control strategy. The objective of the present study was to evaluate the larvicidal activity of the hexane, diethyl ether, ethyl acetate and acetone extracts of <em>Abutilon</em> <em>indicum</em>, <em>Hyptis</em> <em>suaveolens</em> and <em>Leucas</em> <em>aspera</em> against third-stage larvae of <em>Anopheles</em> <em>culicifiacies</em>. The results clearly suggest that all three selected plant extracts exhibited moderate larvicidal activity after 24, 48 and 72 h at 250, 500, 750 and 1000 ppm; the lethal concentrations (LC) at 50% and 90% of <em>A</em>. <em>indicum</em>, <em>H</em>. <em>suaveolens</em> against third instar larvae at 24, 48 and 72 h (hexane, diethyl ether, ethyl acetate and acetone) were as follows: <em>A</em>. <em>indicum</em>, LC₅₀=1031.65, 949.18, 833.58 and 673.68 ppm; LC₉₀=2215.87, 2234.39, 2152.97 and 2455.10 ppm; <em>H.</em> <em>suaveolens</em>, LC₅₀=423.00, 347.50, 236.58 and 217.24 ppm; LC₉₀=1431.91, 1292.15, 1138.49 and 1049.27 ppm and <em>L</em>. <em>aspera</em>, LC₅₀=559.77, 401.56, 299.71 and 263.01 ppm; LC₉₀=1400.80, 1549.31, 1157.96 and 1108.72 ppm at 24 h, respectively. Overall, the highest larvicidal activity was observed with <em>H</em>. <em>suaveolens</em> extract followed by <em>L</em>. <em>aspera</em> and <em>A</em>. <em>indicum</em> at various concentrations at 48 and 72 h, respectively. The objective of this investigation was an attempt to search for a user- and eco-friendly vector control agent. The study proved that the selected plant leaf extracts could serve as potent larvicidal agents against <em>A</em>. <em>culicifacies</em> in vector control programs

Bioefficacy of Morinda tinctoria and Pongamia glabra plant extracts against the malaria vector Anopheles stephensi (Diptera: Culicidae)

Mosquito-borne diseases have an economic impact, including loss in commercial and labour outputs, particularly in countries with tropical and subtropical climates; however, no part of the world is free from vector-borne diseases. The aim of the present study was to investigate the larvicidal, adulticidal and ovicidal activity of dried leaf chloroform, ethyl acetate, acetone, aqueous, and methanol extracts of <em>Morinda</em> <em>tinctoria</em> and <em>Pongamia</em> <em>glabra</em> against larvae of <em>Anopheles</em> <em>stephensi</em> (Diptera: Culicidae). Larvae were exposed to varying concentrations of plant extracts for 24 h. All extracts showed moderate larvicidal effects after 24 h of exposure; however, the highest larval mortality was found with the leaf methanol extracts of <em>M. tinctoria</em> and <em>P. glabra</em> against the larvae of <em>A. stephensi</em> lethal concentration (LC)₅₀=136.24 and 141.05 ppm; LC₉₀=342.67 and 368.89 ppm, respectively. The results of the adulticidal activity assays of chloroform, ethyl acetate, acetone, aqueous, and methanol extracts of <em>M. tinctoria</em> and <em>P. glabra</em> showed significant mortality against larvae of <em>A. stephensi</em>. The methanol extract showed maximum activity compared with the other extracts. The greatest effect on mean percentage hatch in the ovicidal assays was observed 48 h post-treatment. Percent hatch was inversely proportional to the concentration of extract, and directly proportional to the number of eggs. A mortality of 100% was observed with 100-400 ppm methanol extracts and 200-400 ppm aqueous extracts of <em>M. tinctoria</em>, and 200-400 ppm aqueous and methanol extracts of <em>P. glabra</em>. This study provides the first report of the larvicidal, adulticidal and ovicidal activities of <em>M. tinctoria</em> and <em>P. glabra</em> plant extracts against the malaria vector, A. stephensi, representing an ideal eco-friendly approach for its control