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Mosquitoes transmit several diseases which cause millions of deaths every year. The use of synthetic insecticides to control mosquitoes caused diverse effects to the environment, mammals, and high manufacturing cost. The present study was aimed to test the larvicidal activity of green synthesized silver nanoparticles using Annona muricata plant leaf extract against third instar larvae of three medically important mosquitoes, i.e., Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. The different concentrations of green synthesized Ag Nanoparticles (AgNPs; 6, 12, 18, 24, 30 μg mL(-1)) and aqueous crude leaf extract (30, 60, 90, 120, 150 μg mL(-1)) were tested against the larvae for 24 h. Significant larval mortality was observed after the treatment of A. muricata for all mosquitoes with lowest LC50 and LC90 values, viz., A. aegypti (LC50 and LC90 values of 12.58 and 26.46 μg mL(-1)), A. stephensi (LC50 and LC90 values of 15.28 and 31.91 μg mL(-1)) and C. quinquefasciatus (LC50 and LC90 values of 18.77 and 35.72 μg mL(-1)), respectively. The synthesized AgNPs from A. muricata were highly toxic than aqueous crude extract. The nanoparticle characterization was done using spectral and microscopic analysis, namely UV-visible spectroscopy which showed a sharp peak at 420 nm of aqueous medium containing AgNPs, X-ray diffraction (XRD) analysis revealed the average crystalline size of synthesized AgNPs (approximately 45 nm), and Fourier transform infrared spectroscopy (FTIR) study exhibited prominent peaks 3381.28, 2921.03, 1640.17, 1384.58, 1075.83, and 610.77 cm(-1). Particle size analysis (PSA) showed the size and distribution of AgNPs (103 nm); field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) analysis showed a spherical shape, size range from 20 to 53 nm; and energy-dispersive X-ray spectroscopy (EDX) reflects the chemical composition of synthesized AgNPs. Heat stability of the AgNPs was confirmed between the temperatures 20 to 70 °C. The result suggests that green synthesized AgNPs from A. muricata has the potential to be used as a low-cost and eco-friendly approach for the control of selected mosquitoes.

Diseases transmitted by blood-feeding mosquitoes, such as dengue fever, dengue hemorrhagic fever, Japanese encephalitis, malaria, and filariasis, are increasing in prevalence, particularly in tropical and subtropical zones. To control mosquitoes and mosquito-borne diseases, which have worldwide health and economic impacts, synthetic insecticide-based interventions are still necessary, particularly in situations of epidemic outbreak and sudden increases of adult mosquitoes. Green nanoparticle synthesis has been achieved using environmentally acceptable plant extract and eco-friendly reducing and capping agents. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Heliotropium indicum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. Adult mosquitoes were exposed to varying concentrations of aqueous extract of H. indicum and synthesized AgNPs for 24 h. AgNPs were rapidly synthesized using the leaf extract of H. indicum, and the formation of nanoparticles was observed within 6 h. The results recorded from UV-vis spectrum, Fourier transform infrared, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy support the biosynthesis and characterization of AgNPs. The maximum efficacy was observed in synthesized AgNPs against the adult of A. stephensi (lethal dose (LD)₅₀ = 26.712 μg/mL; LD₉₀ = 49.061 μg/mL), A. aegypti (LD₅₀ = 29.626 μg/mL; LD₉₀ = 54.269 μg/mL), and C. quinquefasciatus (LD₅₀ = 32.077 μg/mL; LD₉₀ = 58.426 μg/mL), respectively. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H.indicum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.

Mosquito-borne diseases with an economic impact create loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Extracts from plants may be alternative sources of mosquito control agents because they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products and potentially suitable for use to control mosquitoes. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, in the present study, the adulticidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against adults of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (8, 16, 24, 32, and 40 μg mL(-1)) and aqueous leaf extract (40, 80, 120, 160, and 200 μg mL(-1)) were tested against the adults of A. stephensi, A. aegypti, and C. quinquefasciatus. Adults were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy analysis (EDX), and transmission electron microscopy (TEM). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following lethal dose (LD)₅₀ and LD₉₀ values: A. stephensi had LD₅₀ and LD₉₀ values of 18.041 and 32.575 μg mL(-1); A. aegypti had LD₅₀ and LD₉₀ values of 20.399 and 37.534 μg mL(-1); and C. quinquefasciatus had LD₅₀ and LD₉₀ values of 21.798 and 39.596 μg mL(-1). No mortality was observed in the control. These results suggest that the leaf aqueous extracts of F. elephantum and green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the adulticidal activity of the plant extracts and AgNPs.

Green synthesis technology is one of the rapid, reliable and best routes for the synthesis of silver nanoparticles (AgNPs). There are bioactive compounds with enormous potential in Azadirachta indica (Neem). The extraordinary mosquitoes warrant nanotechnology to integrate with novel molecules. This will be sustainable technology for future. Here, we synthesized AgNPs using aqueous extracts of leaves and bark of Az. indica (Neem). We tested AgNPs as larvicides, pupicides and adulticides against the malaria vector Anopheles stephensi and filariasis vector Culex quinquefasciatus. The results were obtained using UV-visible spectrophotometer and the images were recorded with a transmission electron microscope (TEM). The efficacy tests were then performed at different concentrations varying many hours by probit analysis. The synthesized AgNPs were spherical in shape and with varied sizes (10.47-nm leaf and 19.22-nm bark). The larvae, pupae and adults of filariasis vector C. quinquefasciatus were found to be more susceptible to our AgNPs than the malaria vector An. stephensi. The first and the second instar larvae of C. quinquefasciatus show a mortality rate of 100% after 30 min of exposure. The results against the pupa of C. quinquefasciatus were recorded as LC₅₀ 4 ppm, LC₉₀ 11 ppm and LC₉₉ 13 ppm after 3 h of exposure. In the case of adult mosquitoes, LC₅₀ 1.06 μL/cm(2), LC₉₀ 2.13 μL/cm(2) and LC₉₉ 2.4 μL/cm(2) were obtained after 4 h of exposure. These results suggest that our AgNPs are environment-friendly for controlling malarial and filarial vectors.

Mosquitoes in the larval stage are attractive targets for pesticides because mosquitoes breed in water, and thus, it is easy to deal with them in this habitat. The use of conventional pesticides in the water sources, however, introduces many risks to people and/or the environment. Natural pesticides, especially those derived from plants, are more promising in this aspect. Aromatic plants and their essential oils are very important sources of many compounds that are used in different respects. Insecticides of botanical origin may serve as suitable alternative to chemical insecticides. Acetone, chloroform, ethyl acetate, methanol, and petroleum benzine leaf extracts of Clausena dentata were tested against the fourth instar larvae of Anopheles stephensi, Culex quinquefasciatus, and Aedes aegypti (Diptera: Culicidae). Larval mortality was observed after 24 h of exposure. The highest larval mortality was found in acetone leaf extract, C. quinquefasciatus (LC50 = 0.150278 mg/ml; LC90 = 7.302613 mg/ml), A. aegypti (LC50 = 0.169495 mg/ml; LC90 = 1.10034 mg/ml), and A. stephensi (LC50 = 0.045684 mg/ml; LC90 = 0.045684 mg/ml). GC-MS analysis of plant extracts of acetone solvent revealed 16 compounds, of which the major compounds were benzene,1,2,3-trimethoxy-5-(2-propenyl) (14.97%), Z,Z-6,28-heptatriactontadien-2-one (6.81%), 2-allyl-4-methylphenol (28.14%), 2-allyl-4-methylphenol (17.34%), and 2,6,10,14,18,22-tetracosahexaene, 2,6,10,15,19,23-hexamethyl (10.35%). Our result shows acetone leaf extracts of C. dentata have the potential to be used as an ideal eco-friendly approach for mosquito control.

Some comments have been done on an article describing a pilot trial evaluating the potential use of moxidectin contained in a spot-on formulation in the prevention of canine filarioses in a confined area where the three major canine filariae live in sympatry. We herein present our response to these comments.

Information on the efficacy of pharmaceutical protocols for the prevention of the major canine filarioses (i.e., Dirofilaria immitis, Dirofilaria repens, and Acanthocheilonema reconditum) under natural conditions is scant. Chemoprophylaxis for canine filarioses under field conditions deserves to be studied more fully and information about vector biology, ecology, and seasonality has to be well appreciated to correctly set control protocols. It is advisable that researchers planning field trials to assess the efficacy of any product for the prevention of canine vector-borne diseases should consider different eco-epidemiological aspects of diseases, including their dynamics of transmission, which are driven by complex interactions between animals, pathogens, and vectors.

The elimination of lymphatic filariasis in the Andaman and Nicobar Islands provides unique opportunities and challenges at the same time. Since these islands are remote, are sparsely populated, and have poor transport networks, mass drug administration programs are likely to be difficult to implement. Diurnally subperiodic Wuchereria bancrofti vectored by Downsiomyia nivea was considered for the scope of vector control options. Considering the bioecology of this mosquito, vector control including personal protection measures may not be feasible. However, since these islands are covered by separate administrative machinery which also plays an important role in regulating the food supply, the use of diethylcarbamazine (DEC)-fortified salt as a tool for the interruption of transmission is appealing. DEC-fortified salt has been successfully pilot tested in India and elsewhere, operationally used by China for eliminating lymphatic filariasis. Administration of DEC-fortified salt though simple, rapid, safe, and cost-effective, challenges are to be tackled for translating this precept into action by evolving operationally feasible strategy. Although the use of DEC-fortified salt is conceptually simple, it requires commitment of all sections of the society, an elaborate distribution mechanism that ensures the use of DEC-fortified salt only in the endemic communities, and a vigorous monitoring mechanism. Here, we examine the inbuilt administrative mechanisms to serve the tribal people, health infrastructure, and public distribution system and discuss the prospects of putting in place an operationally feasible strategy for its elimination.

Prior studies have shown that irradiated filarial larvae are developmentally stunted but capable of inducing partial immunity to filariasis in animals. The mechanisms for these effects are poorly understood. Recent studies suggest that intracellular Wolbachia bacteria are necessary for the normal development, reproduction and survival of filarial nematodes. The purpose of this study was to examine the effects of irradiation on Wolbachia in Brugia malayi infective larvae (L3) and on L3 development. The L3 were exposed to 0, 25, 35, 45, 55, 65 or 75 krad of gamma irradiation from a (137) Cesium source and cultured in vitro at 37 degrees C in NCTC/IMDM medium with 10% FCS for 12 days. Irradiation prevented molting of L3 to the L4 stage in a dose-dependent manner. Electron microscopy studies showed that irradiation damaged Wolbachia (25 krad) or cleared them from worm tissues (45 krad). In addition, majority of the irradiated L3s failed to develop the L4 cuticle. Real-time PCR studies showed that irradiation reduced Wolbachia DNA in worm tissues. Parallel in vivo studies confirmed decreased development of irradiated L3 in jirds, with associated effects on Wolbachia. Jirds injected s.c with normal L3 developed antibodies to Wolbachia surface protein (wsp) shortly after the onset of microfilarial patency. In contrast, jirds injected with irradiated L3 did not develop microfilaremia or antibodies to wsp. Additional studies are needed to test the hypothesis that irradiation retards growth and development of filarial L3 by killing Wolbachia.