Filariasis Vector Culex Quinquefasciatus Research Articles

Traditional herbal remedies and dietary spices from Cameroon as novel sources of larvicides against filariasis mosquitoes?

In Cameroon, many dietary spices are used by traditional healers to cure several diseases such as cancer and microbial infections. Aframomum daniellii, Dichrostachys cinerea and Echinops giganteus are Cameroonian spices widely used as flavourings and as food additives. Moreover, they are traditionally herbal remedies employed to treat several diseases, as well as to control populations of insect pests. In this research, we analysed the chemical composition of A. daniellii, D. cinerea and E. giganteus essential oils and we evaluated their larvicidal potential against larvae of the filariasis and West Nile virus vector Culex quinquefasciatus. The essential oils were obtained from different plant parts by hydrodistillation and their composition was analysed by GC-MS. The three spices exhibited different volatile chemical profiles, being characterized by 1,8-cineole, sabinene and β-pinene (A. daniellii), geraniol and terpinen-4-ol (D. cinerea), and silphiperfol-6-ene and presilphiperfolan-8-ol (E. giganteus). Results showed that the highest larvicidal toxicity on Cx. quinquefasciatus was exerted by D. cinerea essential oil (LC50 = 39.1μLL-1), followed by A. daniellii (pericarp essential oil: LC50 = 65.5μLL-1; leaves: LC50 = 65.5μLL-1; seeds: LC50 = 106.5μLL-1) and E. giganteus (LC50 = 227.4μLL-1). Overall, the chance to use the D. cinerea essential oil against Cx. quinquefasciatus young instars seems promising, since it is effective at moderate doses and could be an advantageous alternative to build newer mosquito control tools.

One pot synthesis of silver nanocrystals using the seaweed Gracilaria edulis: biophysical characterization and potential against the filariasis vector Culex quinquefasciatus and the midge Chironomus circumdatus

Mosquitoes (Diptera: Culicidae) represent a deadly threat for millions of humans and animals worldwide. Seaweeds are an important resource for marine biotechnology and are currently investigated as sources of reducing and capping agents for the nanosynthesis of mosquitocides. Culex quinquefasciatus is a major vector of lymphatic filariasis, while chironomid midges (Diptera: Chironomidae) elicit allergic reactions. In this research, silver nanoparticles (AgNP) were biosynthesized using a cheap aqueous extract of Gracilaria edulis as reducing and stabilizing agent. The formation of AgNP was confirmed by UV–Vis spectrophotometry. AgNP were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray analysis. AgNP were mostly spherical and cubic in shape, crystalline in nature. Gracilaria edulis-synthesized AgNP showed excellent ovicidal, larvicidal, pupicidal, and ovideterrent toxicity against Cx. quinquefasciatus and Chironomus circumdatus. Larvicidal LC50 ranged from 17 to 29 ppm. AgNP of 30 ppm led to 100 % mortality in treated eggs. Doses higher than 10 ppm lead to oviposition deterrence rates higher than 75 % (Oviposition Activity Index lower than −0.59). In the field, a single application of AgNP (10 × LC50) led to elimination of larval populations of Cx. quinquefasciatus and Ch. circumdatus within 72 h. Overall, G. edulis-synthesized AgNP may be potential candidates to develop eco-friendly control tools against Diptera of medical and veterinary importance.

Chemical composition of Cinnamosma madagascariensis (Cannelaceae) essential oil and its larvicidal potential against the filariasis vector Culex quinquefasciatus Say

Madagascar flora is diverse and unique. Cinnamosma madagascariensis is an endemic species widely present in the forests of Madagascar. This plant has important traditional uses ranging from management of dementia, epilepsy, headache to malaria. Few data have been reported about the chemical composition of the essential oil, and no studies have been published on its bioactivity against mosquitoes. Here, we focus on the chemical composition of essential oils extracted from C. madagascariensis stem bark and leaves, and their larvicidal potential against the filariasis vector Culex quinquefasciatus. GC-MS analysis revealed differences between the chemical volatile profiles of leaves and bark oils. In the former, linalool (30.1%), limonene (12.0%), myrcene (8.9%) and α-pinene (8.4%) were the major constituents, while in the latter β-pinene (33.3%), α-pinene (19.3%) and limonene (12.0%) were the most representative compounds. Acute toxicity experiments conducted on larvae of the filariasis vector C. quinquefasciatus led to LC50 of 61.6μLL−1 and 80.1μLL−1 for the bark and the leaf essential oils, respectively. Overall, the chance to use compounds from the C. madagascariensis bark and leaf essential oils against filariasis vectors seems promising, since they are effective at moderate doses and could be an advantageous alternative to build newer and safer mosquito control tools. To the best of our knowledge, this is the first report about the chemical composition of C. madagascariensis essential oils.

δ-Cadinene, Calarene and .δ-4-Carene from Kadsura heteroclita Essential Oil as Novel Larvicides Against Malaria, Dengue and Filariasis Mosquitoes.

Mosquitoes (Diptera: Culicidae) are major vectors of important pathogens and parasites. Malaria, dengue fever, yellow fever, filariasis, schistosomiasis and Japanese encephalitis cause millions of deaths every year. Mosquito control is being challenging due to the development of pesticide resistance and negative environmental concerns. In this scenario, plants employed in traditional Asian medicine may be alternative sources of newer and effective mosquitocides. In this research, we evaluated the larvicidal activity of Kadsura heteroclita leaf essential oil (EO) and its major chemical constituents (δ-Cadinene, Calarene and δ-4-Carene) against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. The chemical composition of the EO was analyzed by gas chromatography-mass spectroscopy. GC-MS revealed that the essential oil of K. heteroclita contained 33 compounds. The major chemical components were δ-Cadinene (18.3%), Calarene (14.8%) and δ-4-Carene (12.5%). The EO had a significant toxic effect against early third-stage larvae of An. stephensi, Ae. aegypti and Cx. quinquefasciatus, with LC50 values of 102.86, 111.79 and 121.97 µg/mL. The three major constituents extracted from the K. heteroclita EO were tested individually for acute toxicity against larvae of the three mosquito vectors. δ-Cadinene, Calarene and δ-4-Carene appeared most effective against An. stephensi (LC50 = 8.23, 12.34 and 16.37 µg/mL, r espectively) followed by Ae. aegypti (LC50 = 9.03, 13.33 and 17.91 µg/mL), and Cx. quinquefasciatus (LC50; = 9.86, 14.49 and 19.50 µg/mL). Overall, this study adds knowledge to develop newer and safer natural larvicides against malaria, dengue and filariasis mosquito.

One-pot fabrication of silver nanocrystals using Ormocarpum cochinchinense: Biophysical characterization of a potent mosquitocidal and toxicity on non-target mosquito predators

Mosquito vectors (Diptera: Culicidae) are vectors of pathogens and parasites of public health importance, including malaria, dengue, chikungunya, Japanese encephalitis, lymphatic filariasis and Zika virus. Novel eco-friendly control tools against Culicidae are a priority. In this research, silver nanoparticles (Ag NPs) were rapidly synthesized using the aqueous leaf extract of Ormocarpum cochinchinense as a cheap, non-toxic material. The bio-reduced Ag NPs were characterized by UV–visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX) and X-ray diffraction analysis (XRD). The acute toxicity of O. cochinchinense leaf extract and synthesized Ag NP was evaluated against larvae of the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. Compared to the leaf aqueous extract, synthesized Ag NPs showed high toxicity against A. stephensi, A. aegypti and C. quinquefasciatus, with LC50 values of 10.43, 11.26 and 12.35μg/mL, respectively. Synthesized Ag NPs were found safer to non-target mosquito predators Diplonychus indicus and Gambusia affinis, with LC50 values ranging from 522.13 to 637.70μg/mL. Overall, this study firstly shed light to O. cochinchinense's potential as a bioresource for rapid, cheap and effective nanosynthesis of mosquitocides.

One-step synthesis of polydispersed silver nanocrystals using Malva sylvestris: an eco-friendly mosquito larvicide with negligible impact on non-target aquatic organisms.

The synthesis of eco-friendly nanoparticles is evergreen branch of nanoscience with a growing number of biomedical implications. In this study, we investigated the synthesis of polydisperse and stable silver nanoparticles (AgNP) using a cheap leaf extract of Malva sylvestris (Malvaceae). Bio-reduced AgNP were characterized by UV-visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The acute toxicity of M. sylvestris leaf extract and green-synthesized AgNP was evaluated against larvae of the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti and the filariasis vector Culex quinquefasciatus. Compared to the leaf aqueous extract, AgNP showed higher toxicity against A. stephensi, A. aegypti, and C. quinquefasciatus with LC50 values of 10.33, 11.23, and 12.19μg/mL, respectively. Green-synthesized AgNP were found safer to non-target organisms Diplonychus indicus and Gambusia affinis, with respective LC50 values ranging from 813.16 to 1044.52μg/mL. Overall, this research firstly shed light on the mosquitocidal potential of M. sylvestris, a potential bio-resource for rapid, cheap and effective synthesis of polydisperse and highly stable silver nanocrystals.

Chemical composition, toxicity and non-target effects of Pinus kesiya essential oil: An eco-friendly and novel larvicide against malaria, dengue and lymphatic filariasis mosquito vectors

Mosquitoes (Diptera: Culicidae) are vectors of important parasites and pathogens causing death, poverty and social disability worldwide, with special reference to tropical and subtropical countries. The overuse of synthetic insecticides to control mosquito vectors lead to resistance, adverse environmental effects and high operational costs. Therefore, the development of eco-friendly control tools is an important public health challenge. In this study, the mosquito larvicidal activity of Pinus kesiya leaf essential oil (EO) was evaluated against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti and the lymphatic filariasis vector Culex quinquefasciatus. The chemical composition of the EO was analyzed by gas chromatography–mass spectroscopy. GC–MS revealed that the P. kesiya EO contained 18 compounds. Major constituents were α-pinene, β-pinene, myrcene and germacrene D. In acute toxicity assays, the EO showed significant toxicity against early third-stage larvae of An. stephensi, Ae. aegypti and Cx. quinquefasciatus, with LC50 values of 52, 57, and 62µg/ml, respectively. Notably, the EO was safer towards several aquatic non-target organisms Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC50 values ranging from 4135 to 8390µg/ml. Overall, this research adds basic knowledge to develop newer and safer natural larvicides from Pinaceae plants against malaria, dengue and filariasis mosquito vectors.

Larvicidal and repellent potential of Zingiber nimmonii (J. Graham) Dalzell (Zingiberaceae) essential oil: an eco-friendly tool against malaria, dengue, and lymphatic filariasis mosquito vectors?

Mosquitoes (Diptera: Culicidae) are important vectors of terms of public health relevance, especially in tropical and sub-tropical regions. The continuous and indiscriminate use of conventional pesticides for the control of mosquito vectors has resulted in the development of resistance and negative impacts on non-target organisms and the environment. Therefore, there is a need for development of effective mosquito control tools. In this study, the larvicidal and repellent activity of Zingiber nimmonii rhizome essential oil (EO) was evaluated against the malaria vector Anopheles stephensi, the dengue vector Aedes aegypti, and the lymphatic filariasis vector Culex quinquefasciatus. The chemical composition of the EO was analyzed by gas chromatography-mass spectroscopy (GC-MS). GC-MS revealed that the Z. nimmonii EO contained at least 33 compounds. Major constituents were myrcene, β-caryophyllene, α-humulene, and α-cadinol. In acute toxicity assays, the EO showed significant toxicity against early third-stage larvae of An. stephensi, Ae. aegypti, and Cx. quinquefasciatus, with LC50 values of 41.19, 44.46, and 48.26μg/ml, respectively. Repellency bioassays at 1.0, 2.0, and 5.0mg/cm(2) of Z. nimmonii EO gave 100% protection up to 120, 150, and 180min. against An. stephensi, followed by Ae. aegypti (90, 120, and 150min) and Cx. quinquefasciatus (60, 90, and 120min). Furthermore, the EO was safer towards two non-target aquatic organisms, Diplonychus indicus and Gambusia affinis, with LC50 values of 3241.53 and 9250.12μg/ml, respectively. Overall, this research adds basic knowledge to develop newer and safer natural larvicides and repellent from Zingiberaceae plants against malaria, dengue, and filariasis mosquito vectors.

Larvicidal potential of carvacrol and terpinen-4-ol from the essential oil of Origanum vulgare (Lamiaceae) against Anopheles stephensi, Anopheles subpictus, Culex quinquefasciatus and Culex tritaeniorhynchus (Diptera: Culicidae)

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. However, the use of synthetic insecticides to control Culicidae may lead to resistance, high operational costs and adverse non-target effects. Nowadays, plant-borne mosquitocides may serve as suitable alternative in the fight against mosquito vectors. In this study, the mosquito larvicidal activity of Origanum vulgare (Lamiaceae) leaf essential oil (EO) and its major chemical constituents was evaluated against the malaria vectors Anopheles stephensi and An. subpictus, the filariasis vector Culex quinquefasciatus and the Japanese encephalitis vector Cx. tritaeniorhynchus. The chemical composition of the EO was analyzed by gas chromatography–mass spectroscopy. GC–MS revealed that the essential oil of O. vulgare contained 17 compounds. The major chemical components were carvacrol (38.30%) and terpinen-4-ol (28.70%). EO had a significant toxic effect against early third-stage larvae of An. stephensi, An. subpictus, Cx. quinquefasciatus and Cx. tritaeniorhynchus, with LC50 values of 67.00, 74.14, 80.35 and 84.93μg/ml. The two major constituents extracted from the O. vulgare EO were tested individually for acute toxicity against larvae of the four mosquito vectors. Carvacrol and terpinen-4-ol appeared to be most effective against An. stephensi (LC50=21.15 and 43.27μg/ml, respectively) followed by An. subpictus (LC50=24.06 and 47.73μg/ml), Cx. quinquefasciatus (LC50=26.08 and 52.19μg/ml) and Cx. tritaeniorhynchus (LC50=27.95 and 54.87μg/ml). Overall, this research adds knowledge to develop newer and safer natural larvicides against malaria, filariasis and Japanese encephalitis mosquito vectors.

Carbon and silver nanoparticles in the fight against the filariasis vector Culex quinquefasciatus: genotoxicity and impact on behavioral traits of non-target aquatic organisms.

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. The Culex genus, with special reference to Culex quinquefasciatus, comprises the most common vectors of filariasis across urban and semi-urban areas of Asia. In recent years, important efforts have been conducted to propose green-synthesized nanoparticles as a valuable alternative to synthetic insecticides. However, the mosquitocidal potential of carbon nanoparticles has been scarcely investigated. In this study, the larvicidal and pupicidal activity of carbon nanoparticle (CNP) and silver nanoparticle (AgNP) was tested against Cx. quinquefasciatus. UV-Vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, and Raman analysis confirmed the rapid and cheap synthesis of carbon and silver nanoparticles. In laboratory assays, LC50 (lethal concentration that kills 50 % of the exposed organisms) values ranged from 8.752 ppm (first-instar larvae) to 18.676 ppm (pupae) for silver nanoparticles and from 6.373 ppm (first-instar larvae) to 14.849 ppm (pupae) for carbon nanoparticles. The predation efficiency of the water bug Lethocerus indicus after a single treatment with low doses of silver and carbon nanoparticles was not reduced. Moderate evidence of genotoxic effects induced by exposure to carbon nanoparticles was found on non-target goldfish, Carassius auratus. Lastly, the plant extract used for silver nanosynthesis was tested for 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity. Overall, our results pointed out that AgNP and CNP can be a candidate for effective tools to reduce larval and pupal populations of filariasis vectors, with reduced genotoxicity and impact on behavioral traits of other aquatic organisms sharing the same ecological niche of Cx. quinquefasciatus.

Toxicity of seaweed-synthesized silver nanoparticles against the filariasis vector Culex quinquefasciatus and its impact on predation efficiency of the cyclopoid crustacean Mesocyclops longisetus.

Nearly 1.4 billion people in 73 countries worldwide are threatened by lymphatic filariasis, a parasitic infection that leads to a disease commonly known as elephantiasis. Filariasis is vectored by mosquitoes, with special reference to the genus Culex. The main control tool against mosquito larvae is represented by treatments with organophosphates and insect growth regulators, with negative effects on human health and the environment. Recently, green-synthesized nanoparticles have been proposed as highly effective larvicidals against mosquito vectors. In this research, we attempted a reply to the following question: do green-synthesized nanoparticles affect predation rates of copepods against mosquito larvae? We proposed a novel method of seaweed-mediated synthesis of silver nanoparticles using the frond extract of Caulerpa scalpelliformis. The toxicity of the seaweed extract and silver nanoparticles was assessed against the filarial vector Culex quinquefasciatus. Then, we evaluated the predatory efficiency of the cyclopoid crustacean Mesocyclops longisetus against larval instars of C. quinquefasciatus in a nanoparticle-contaminated water environment. Green-synthesized silver nanoparticles were characterized by UV-vis spectrum, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In mosquitocidal assays, the LC₅₀ values of the C. scalpelliformis extract against C. quinquefasciatus were 31.38 ppm (I), 46.49 ppm (II), 75.79 ppm (III), 102.26 ppm (IV), and 138.89 ppm (pupa), while LC₅₀ of silver nanoparticles were 3.08 ppm, (I), 3.49 ppm (II), 4.64 ppm (III), 5.86 ppm (IV), and 7.33 ppm (pupa). The predatory efficiency of the copepod M. longisetus in the control treatment was 78 and 59% against I and II instar larvae of C. quinquefasciatus. In a nanoparticle-contaminated environment, predation efficiency was 84 and 63%, respectively. Predation was higher against first instar larvae over other instars. Overall, our study showed that seaweed-synthesized silver nanoparticles can be proposed in synergy with biological control agents against Culex larvae, since their use leads to little detrimental effects against aquatic predators, such as copepods.

Risk factors for the presence of chikungunya and dengue vectors (Aedes aegypti and Aedes albopictus), their altitudinal distribution and climatic determinants of their abundance in central Nepal.

BackgroundThe presence of the recently introduced primary dengue virus vector mosquito Aedes aegypti in Nepal, in association with the likely indigenous secondary vector Aedes albopictus, raises public health concerns. Chikungunya fever cases have also been reported in Nepal, and the virus causing this disease is also transmitted by these mosquito species. Here we report the results of a study on the risk factors for the presence of chikungunya and dengue virus vectors, their elevational ceiling of distribution, and climatic determinants of their abundance in central Nepal.Methodology/Principal FindingsWe collected immature stages of mosquitoes during six monthly cross-sectional surveys covering six administrative districts along an altitudinal transect in central Nepal that extended from Birgunj (80 m above sea level [asl]) to Dhunche (highest altitude sampled: 2,100 m asl). The dengue vectors Ae. aegypti and Ae. albopictus were commonly found up to 1,350 m asl in Kathmandu valley and were present but rarely found from 1,750 to 2,100 m asl in Dhunche. The lymphatic filariasis vector Culex quinquefasciatus was commonly found throughout the study transect. Physiographic region, month of collection, collection station and container type were significant predictors of the occurrence and co-occurrence of Ae. aegypti and Ae. albopictus. The climatic variables rainfall, temperature, and relative humidity were significant predictors of chikungunya and dengue virus vectors abundance.Conclusions/SignificanceWe conclude that chikungunya and dengue virus vectors have already established their populations up to the High Mountain region of Nepal and that this may be attributed to the environmental and climate change that has been observed over the decades in Nepal. The rapid expansion of the distribution of these important disease vectors in the High Mountain region, previously considered to be non-endemic for dengue and chikungunya fever, calls for urgent actions to protect the health of local people and tourists travelling in the central Himalayas.

Silver nanoparticles: a possibility for malarial and filarial vector control technology.

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.

Spatio-temporal distribution of dengue and lymphatic filariasis vectors along an altitudinal transect in Central Nepal.

BackgroundRapidly increasing temperatures in the mountain region of Nepal and recent reports of dengue fever and lymphatic filariasis cases from mountainous areas of central Nepal prompted us to study the spatio-temporal distribution of the vectors of these two diseases along an altitudinal transect in central Nepal.Methodology/Principal FindingsWe conducted a longitudinal study in four distinct physiographical regions of central Nepal from September 2011 to February 2012. We used BG-Sentinel and CDC light traps to capture adult mosquitoes. We found the geographical distribution of the dengue virus vectors Aedes aegypti and Aedes albopictus along our study transect to extend up to 1,310 m altitude in the Middle Mountain region (Kathmandu). The distribution of the lymphatic filariasis vector Culex quinquefasciatus extended up to at least 2,100 m in the High Mountain region (Dhunche). Statistical analysis showed a significant effect of the physiographical region and month of collection on the abundance of A. aegypti and C. quinquefasciatus only. BG-Sentinel traps captured significantly higher numbers of A. aegypti than CDC light traps. The meteorological factors temperature, rainfall and relative humidity had significant effects on the mean number of A. aegypti per BG-Sentinel trap. Temperature and relative humidity were significant predictors of the number of C. quinquefasciatus per CDC light trap. Dengue fever and lymphatic filariasis cases had previously been reported from all vector positive areas except Dhunche which was free of known lymphatic filariasis cases.Conclusions/SignificanceWe conclude that dengue virus vectors have already established stable populations up to the Middle Mountains of Nepal, supporting previous studies, and report for the first time the distribution of lymphatic filariasis vectors up to the High Mountain region of this country. The findings of our study should contribute to a better planning and scaling-up of mosquito-borne disease control programmes in the mountainous areas of Nepal.

Green nanoparticles for mosquito control.

Here, we have used the green method for synthesis of silver and gold nanoparticles. In the present study the silver (Ag) and gold (Au) nanoparticles (NPs) were synthesized by using the aqueous bark extract of Indian spice dalchini (Cinnamomum zeylanicum) (C. zyelanicum or C. verum J. Presl). Additionally, we have used these synthesized nanoparticles for mosquito control. The larvicidal activity has been tested 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 and varying numbers of hours by probit analysis. The synthesized AgNPs were in spherical shape and average sizes (11.77 nm AgNPs and 46.48 nm AuNPs). The larvae of An. stephensi were found highly susceptible to the synthesized AgNPs and AuNPs than the Cx. quinquefasciatus. These results suggest that the C. zeylanicum synthesized silver and gold nanoparticles have the potential to be used as an ideal ecofriendly approach for the control of mosquito.

Monitoring of malaria, Japanese encephalitis and filariasis vectors

BackgroundVector monitoring in military stations would help in protecting the armed forces from vector borne diseases such as malaria, Japanese encephalitis and filariasis. MethodsAdult mosquitoes were collected from four villages around a military station in India using light traps and the species composition was estimated. Insecticide susceptibility of disease vectors against DDT, deltamethrin and permethrin was established using WHO kits. ResultsThe known malaria vectors constituted 4.9% of the total mosquito collections and Anopheles philippinensis/nivipes (2.05%) was the most abundant. Japanese encephalitis and dengue vectors constituted 25.3 and 0.05% whereas the known vectors of both Japanese encephalitis and filariasis formed 50.9%. The mean (±SEmean) of annual parasitic index, slide positivity and Plasmodium falciparum percentage among the civilian population during the study period were 1.46 ± 0.37, 1.65 ± 0.77 and 50.2 ± 10.7. The filariasis vector Culex quinquefasciatus was resistant to DDT with 65.4% mortality whereas the DDT resistance in the Japanese encephalitis vector Culex vishnui gr. with 91.9% mortality needs to be confirmed. All other species tested were susceptible to DDT, deltamethrin and permethrin. ConclusionTargeted interventions are needed to reduce the disease burden and vector activity in the villages adjoining the military station. The use of insect repellents, bed nets and repellent impregnated uniforms by the troops should be ensured for protection from vector borne diseases.

Fungal-mediated nano silver: an effective adulticide against mosquito

Fungi as such are known to be an effective mosquito control agent. In the present investigation, the effect of silver nanoparticles synthesized with Chrysosporium keratinophilum, Verticillium lecanii, and Fusarium oxysporum f.sp. pisi has been evaluated against the adult mosquito of filariasis vector Culex quinquefasciatus. The silver nanoparticles were characterized by using the UV-Vis spectrophotometer and X-ray diffraction techniques. The micrographs of silver nanoparticles were obtained by transmission electron microscope and scanning electron microscope. Elemental analysis on single particle was carried out by EDX analysis. The characterization study confirmed different shapes and sizes of silver nanoparticles. The efficacy test was performed at five different concentrations for a period of 24 h by the probit analysis. The C. quinquefasciatus has shown higher efficacy against the silver nanoparticles synthesized with C. keratinophilum and V. lecanii (lethal concentration (LC)(50) 0.19 and 0.4 μl/cm(2); LC(90) 2.4 and 3.2 μl/cm(2); and LC(99) 4.0 and 5.6 μl/cm(2)) after 22 h of exposure. While the silver nanoparticles synthesized with F. oxysporum f.sp. pisi were found to be less effective against the C. quinquefasciatus, the silver nanoparticles synthesized by C. keratinophilum and V. lecanii were found to be more effective than those generated with the help of F. oxysporum f.sp. pisi and C. quinquefasciatus. The use of fungus-mediated silver nanoparticles is a rapid, environmentally safer, and greener approach for vector control strategy and is adaptable globally.

Mosquito larvicidal and ovicidal activity of Delonix elata (L.) Gamble against Culex quinquefasciatus Say (Diptera: Culicidae)

ObjectiveTo determine the larvicidal and ovicidal efficacy of different solvent leaf and seed extract of Delonix elata (D. elata) against filariasis vector Culex quinquefasciatus (Cx. quinquefasciatus). MethodsTwenty five early third instar larvae of Cx. quinquefasciatus were exposed to various concentrations and were assayed in the laboratory by using the protocol of WHO 2005. The larval mortality was observed after 24 h of treatment. The ovicidal activity was determined against Cx. quinquefasciatus mosquito to various concentrations ranging from 75-600 mg/L under the laboratory conditions. ResultsAmong five solvent extracts tested the maximum efficacy was observed in the leaf and seed methanol extracts. The LC50 and LC90 values of D. elata against early third instar of Cx. quinquefasciatus were 124.84, 147.86 mg/L and 213.88, 289.43 mg/L, respectively. No mortality was observed in controls. The Chi-square values were significant at P<0.05 level. Among five tested solvent, methanol extract was found to be most effective for ovicidal activity against Cx. quinquefasciatus mosquito. 100% mortality was observed at 375 mg/L . ConclusionsFrom the results it can be concluded the crude extract of D. elata was an excellent potential for controlling Cx. quinquefasciatus mosquito larvae and eggs.

Larvicidal efficacy of Adhatoda vasica (L.) Nees against the bancroftian filariasis vector Culex quinquefasciatus Say and dengue vector Aedes aegypti L. in in vitro condition

The larvicidal activities of methanolic fractions from Adhatoda vasica leaf extracts were investigated against the bancroftian filariasis vector Culex quinquefasciatus and dengue vector Aedes aegypti. The results indicated that the mortality rates was high at 100, 150, 200 and 250 ppm of methanol extract of fractions III with R (f) value 0.67 and methanol extract of fraction V with R (f) value 0.64 of A. vasica against all the larval instars of C. quinquefasciatus and A. aegypti. The result of log probit analysis (at 95% confidence level) revealed that lethal concentration, LC(50) and LC(90) values were 106.13 and 180.6 ppm for fraction III, 110.6 and 170 ppm for fraction V of C. quinquefasciatus. And, the LC(50) and LC(90) values were 157.5 and 215.5 ppm for fraction III of A. aegypti and 120 and 243.5 ppm for the fraction V of A. aegypti, respectively. All the tested fractions proved to have strong larvicidal activity (doses from 100 to 250 ppm) against C. quinquefasciatus and A. aegypti. In general, second instar was more susceptible than the later instar. The results achieved suggest that, in addition to their ethnopharmacology value, A. vasica may also serve as a natural larvicidal agent.

Efficacy of Bacillus sphaericus in control of the filariasis vector Culex quinquefasciatus in an urban area of Olinda, Brazil

The efficacy of Bacillus sphaericus 2362 against Culex quinquefasciatus was tested in 1991–1994 in a major Brazilian endemic zone for bancroftian filariasis. Continuous selection pressure against the mosquito population was sustained for 18 months through treatment of 2500 potential breeding sites occurring within a 5.7-km 2 urban area in the Metropolitan Region of Recife. The impact of this control intervention was evaluated by comparing entomological indices with those from an untreated area. Application of the larvicide kept the Cx. quinquefasciatus population density significantly lower when compared to the untreated area, despite some operational difficulties. Adult densities remained lower for at least 5 months after spraying ceased. Pre-trial microfilaria rates from the untreated and operational area were 13.1% and 7.2%, respectively. A 60% reduction in human exposure to infective bites was recorded as a consequence of this vector population control.