Larvicidal efficacy of Catharanthus roseus Linn. (Family: Apocynaceae) leaf extract and bacterial insecticide Bacillus thuringiensis against Anopheles stephensi Liston.

AbstractObjectiveTo explore the larvicidal activity of Catharanthus roseus (C. roseus) leaf extract and Bacillus thuringiensis (B. thuringiensis) against the malarial vector Anopheles stephensi (An. stephensi), when being used alone or together.MethodsThe larvicidal activity was assayed at various concentrations under the laboratory and field conditions. The LC50 and LC90 values of the C. roseus leaf extract were determined by probit analysis.ResultsThe plant extract showed larvicidal effects after 24 h of exposure; however, the highest larval mortality was found in the petroleum ether extract of C. roseus against the first to fourth instars larvae with LC50=3.34, 4.48, 5.90 and 8.17 g/L, respectively; B. thuringiensis against the first to fourth instars larvae with LC50=1.72, 1.93, 2.17 and 2.42 g/L, respectively; and the combined treatment with LC50=2.18, 2.41, 2.76 and 3.22 g/L, respectively. No mortality was observed in the control.ConclusionsThe petroleum ether extract of C. roseus extract and B. thuringiensis have potential to be used as ideal eco–friendly agents for the control of An. stephensi in vector control programs. The combined treatment with this plant crude extract and bacterial toxin has better larvicidal efficacy against An. stephensi

Neem by-products in the fight against mosquito-borne diseases: Biotoxicity of neem cake fractions towards the rural malaria vector Anopheles culicifacies (Diptera: Culicidae)

Objective: To evaluate the ovicidal, larvicidal and adulticidal potential of neem cake fractions of different polarity against the rural malaria vector Anopheles culicifacies (An. culicifacies). Methods: Neem cake fractions' total methanol extract (NTMeOH), total ethyl acetate extract (NTAcOEt), ethyl acetate fraction after repartition with NTMeOH (NRAcOEt), butanol fraction after repartition with NTMeOH (NRBuOH), and aqueous fraction after repartition of NTMeOH (NRH2O) were tested against An. culicifacies eggs, fourth instar larvae and adults. Results: In larvicidal experiments, NTMeOH, NTAcOEt, NRAcOEt, NRBuOH and NRH2O achieved LC50 values of 1.32, 1.50, 1.81, 1.95 and 2.54 mg/L, respectively. All fractions tested at 150 mg/L were able to reduce egg hatchability of more than 50%, with the exception of NTAcOEt and NRAcOEt. In adulticidal assays, NTMeOH, NTAcOEt, NRAcOEt, NRBuOH and NRH2O achieved LC50 values of 3.01, 2.95, 3.23, 3.63 and 3.00 mg/L, respectively. Conclusions: Overall, this study suggests that the methanolic fractions of neem cake may be considered as a new and cheap source of highly effective compounds against the rural malaria vector An. culicifacies

Clerodendrum chinense-mediated biofabrication of silver nanoparticles: Mosquitocidal potential and acute toxicity against non-target aquatic organisms

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. However, the use of synthetic insecticides to control Culicidae may lead to high operational costs and adverse non-target effects. Plant-borne compounds have been proposed for rapid extracellular synthesis of mosquitocidal nanoparticles. Their impact against biological control agents of mosquito larval populations has been poorly studied. In this study, we synthesized silver nanoparticles (Ag NPs) using the Clerodendrum chinense leaf extract as reducing and stabilizing agent. The biosynthesis of AgNP was confirmed analyzing the excitation of surface Plasmon resonance using ultraviolet-visible (UV-vis) spectrophotometry. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the clustered and irregular shapes of Ag NP. The presence of silver was determined by energy dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy analysis investigated the identity of secondary metabolites, which may act as Ag NP capping agents. The acute toxicity of C. chinense leaf extract and biosynthesized Ag NP was evaluated against larvae of Anopheles subpictus, Aedes albopictus and Culex tritaeniorhynchus. Compared to the leaf aqueous extract, biosynthesized Ag NP showed higher toxicity against A. subpictus, A. albopictus, and C. tritaeniorhynchus with LC50 values of 10.23, 11.10 and 12.38μg/mL, respectively. Biosynthesized Ag NPs were found safer to non-target organisms Diplonychus indicus, Anisops bouvieri and Gambusia affinis, with respective LC50 values ranging from 647.05 to 6877.28μg/ml. Overall, our results highlight that C. chinense-fabricated Ag NP are a promising and eco-friendly tool against larval populations of mosquito vectors of medical and veterinary importance, with negligible toxicity against non-target aquatic organisms

Green-synthesized silver nanoparticles using Psychotria nilgiriensis: toxicity against the dengue vector Aedes aegypti (Diptera: Culicidae) and impact on the predatory efficiency of the non-target organism Poecilia sphenops (Cyprinodontiformes: Poeciliidae)

Mosquitoes transmit serious diseases to humans and animals, causing millions of deaths every year. Effective insecticides of natural origin for eco-friendly vector control are a priority. In this study, silver nanoparticles (AgNPs) biosynthesized using as cheap Psychotria nilgiriensis leaf extract were tested on larvae and pupae of Aedes aegypti (Diptera: Culicidae). Biophysical characterization was carried out with UV–vis spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Larvae were exposed to varying concentrations of aqueous extract of synthesized AgNPs for 24 h. The maximum mortality was observed for green-synthesized AgNPs. Moreover, the combined treatment of leaf extract of P. nilgiriensis and AgNPs lowered the plant extract LC50 to 92.87, 115.27, 140.37, 169.30 and 212.55 μg/ml. The effectiveness of green synthesized AgNPs was confirmed against eggs and adults of A. aegypti. Furthermore, we showed that the predatory efficiency of Poecilia sphenops on A. aegypti was not reduced after the exposure at sublethal doses of AgNPs. Predation in the control was 65% (larva I) and 49.62% (larva II). Predation against late-instar larvae was minimal. In AgNPs-treated environment (3 ppm), predation was boosted to 90.25% (larva I) and 76.50% (larva II), respectively. Overall, P. nilgiriensis-synthesized AgNPs could be proposed at ultra-low doses to reduce larval population of dengue vectors enhancing predation rates of P. sphenops

Swift Fabrication of Silver Nanoparticles Using Bougainvillea glabra: Potential Against the Japanese Encephalitis Vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae)

Mosquitoes are the most critical group of insects in the context of public health, since they transmit key parasites and pathogens, causing millions of deaths annually. Culex tritaeniorhynchus is an important vector of Japanese encephalitis (JE) across urban and semi-urban areas of Asia. In this study, we bio-fabricated silver nanoparticles (Ag NP) using the leaf extract of Bougainvillea glabra as reducing and stabilizing agent. The synthesis of Ag NP was confirmed analyzing the excitation of surface Plasmon resonance using ultraviolet–visible (UV–vis) spectrophotometry. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the clustered and irregular shapes of Ag NP. The presence of silver was determined by energy dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy analysis investigated the identity of secondary metabolites, which may act as Ag NP capping agents. The acute toxicity of B. glabra extract, synthesized Ag NP and a combined treatment testing blends of both mosquitocidals was evaluated against larvae and pupae of Cx. tritaeniorhynchus.B. glabra showed LC50 of 198.93 (larva I), 234.50 (II), 309.18 (III), 371.69 (IV) and 466.09 (pupa) µg/ml, Ag NP LC50 ranged from 7.77 (I) to 19.44 µg/ml (pupa). Combined treatments with B. glabra leaf extract plus 5.12.5 µg/ml of Ag NP lowered the botanical LC50 to 66.09 (I), 76.48 (II), 99.02 (III), 133.43 (IV) and 179.74 µg/ml (IV), respectively. The effectiveness of green-fabricated Ag NP against the JE vector was confirmed in adulticidal tests, as well as evaluating the impact of Ag NP on fecundity and longevity of adult mosquitoes. Lastly, the larvicidal effectiveness of Ag NP was confirmed in the field, treating sewage water bodies. Overall, this study suggests that the green-synthesized Ag NP fabricated using B. glabra can be considered a potential mosquito control device against the JE vector, C. tritaeniorhynchus in Asian regions

Neem cake as a promising larvicide and adulticide against the rural malaria vector Anopheles culicifacies (Diptera: Culicidae). A HPTLC fingerprinting approach

Mosquitoes are insects of huge public health importance, since they act as vectors for important pathogens and parasites. Here, we focused on the possibility of using the neem cake in the fight against mosquito vectors. The neem cake chemical composition significantly changes among producers, as evidenced by our HPTLC (High performance thin layer chromatography) analyses of different marketed products. Neem cake extracts were tested to evaluate the ovicidal, larvicidal and adulticidal activity against the rural malaria vector Anopheles culicifacies. Ovicidal activity of both types of extracts was statistically significant, and 150 ppm completely inhibited egg hatching. LC50 values were extremely low against fourth instar larvae, ranging from 1.321 (NM1) to 1.818 ppm (NA2). Adulticidal activity was also high, with LC50 ranging from 3.015 (NM1) to 3.637 ppm (NM2). This study pointed out the utility of neem cake as a source of eco-friendly mosquitocides in Anopheline vector control programmes

Biosynthesis, characterization, and acute toxicity of Berberis tinctoria-fabricated silver nanoparticles against the Asian tiger mosquito, Aedes albopictus, and the mosquito predators Toxorhynchites splendens and Mesocyclops thermocyclopoides

Aedes albopictus is an important arbovirus vector, including dengue. Currently, there is no specific treatment for dengue. Its prevention solely depends on effective vector control measures. In this study, silver nanoparticles (AgNPs) were biosynthesized using a cheap leaf extract of Berberis tinctoria as reducing and stabilizing agent and tested against Ae. albopictus and two mosquito natural enemies. AgNPs were characterized by using UV–vis spectrophotometry, X-ray diffraction, and scanning electron microscopy. In laboratory conditions, the toxicity of AgNPs was evaluated on larvae and pupae of Ae. albopictus. Suitability Index/Predator Safety Factor was assessed on Toxorhynchites splendens and Mesocyclops thermocyclopoides. The leaf extract of B. tinctoria was toxic against larval instars (I–IV) and pupae of Ae. albopictus; LC50 was 182.72 ppm (I instar), 230.99 ppm (II), 269.65 ppm (III), 321.75 ppm (IV), and 359.71 ppm (pupa). B. tinctoria-synthesized AgNPs were highly effective, with LC50 of 4.97 ppm (I instar), 5.97 ppm (II), 7.60 ppm (III), 9.65 ppm (IV), and 14.87 ppm (pupa). Both the leaf extract and AgNPs showed reduced toxicity against the mosquito natural enemies M. thermocyclopoides and T. splendens. Overall, this study firstly shed light on effectiveness of B. tinctoria-synthesized AgNPs as an eco-friendly nanopesticide, highlighting the concrete possibility to employ this newer and safer tool in arbovirus vector control programs

Multipurpose effectiveness of Couroupita guianensis-synthesized gold nanoparticles: high antiplasmodial potential, field efficacy against malaria vectors and synergy with Aplocheilus lineatus predators

Mosquito-bornediseasesrepresentadeadlythreatfor millions of people worldwide. According to recent estimates, about 3.2 billion people, almost half of the world’s population, areat risk of malaria.Malariacontrol is particularly challenging due to a growing number of chloroquine-resistant Plasmodium and pesticide-resistant Anopheles vectors. Newer andsafer control tools are required. In this research, gold nanoparticles (AuNPs) were biosynthesized using a cheap flower extract of Couroupita guianensis as reducing and stabilizing agent. The biofabrication of AuNP was confirmed by UV–vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), zeta potential, andparticlesizeanalysis.AuNPshoweddifferentshapesincluding spheres, ovals, and triangles. AuNPs were crystalline in nature with face-centered cubic geometry; mean size was 29.2–43.8 nm. In laboratory conditions, AuNPs were toxic against Anopheles stephensi larvae, pupae, and adults. LC 50 was17.36ppm(larvaI),19.79ppm(larvaII),21.69ppm(larva III), 24.57 ppm (larva IV), 28.78 ppm (pupa), and 11.23 ppm (adult).Inthefield,asingletreatmentwith C.guianensis flower extract and AuNP (10×LC50) led to complete larval mortality after 72 h. In standard laboratory conditions, the predation efficiency of golden wonder killifish, Aplocheilus lineatus, against A. stephensi IV instar larvae was 56.38 %, while in an aquatic environment treated with sub-lethal doses of the flower extract or AuNP, predation efficiency was boosted to 83.98 and 98.04 %, respectively. Lastly, the antiplasmodial activity of C. guianensis flower extract and AuNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. IC 50 of C. guianensis flower extract was 43.21 μg/ml (CQ-s) and 51.16 μg/ml (CQ-r). AuNP IC50 was 69.47 μg/ml (CQ-s) and 76.33 μg/ml (CQ-r). Overall, our results showed the multipurpose effectiveness of C. guianensissynthesized AuNPs, since they may be proposed as newer and safer tools in the fight against CQ-r strains of P. falciparum and for field control of malaria vectors, in synergy with wonder killifish predators

Multipurpose effectiveness of Couroupita guianensis-synthesized gold nanoparticles: high antiplasmodial potential, field efficacy against malaria vectors and synergy with Aplocheilus lineatus predators

Mosquito-borne diseases represent a deadly threat for millions of people worldwide. According to recent estimates, about 3.2 billion people, almost half of the world’s population, are at risk of malaria. Malaria control is particularly challenging due to a growing number of chloroquine-resistant Plasmodium and pesticide-resistant Anopheles vectors. Newer and safer control tools are required. In this research, gold nanoparticles (AuNPs) were biosynthesized using a cheap flower extract of Couroupita guianensis as reducing and stabilizing agent. The biofabrication of AuNP was confirmed by UV–vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), zeta potential, and particle size analysis. AuNP showed different shapes including spheres, ovals, and triangles. AuNPs were crystalline in nature with face-centered cubic geometry; mean size was 29.2–43.8 nm. In laboratory conditions, AuNPs were toxic against Anopheles stephensi larvae, pupae, and adults. LC50 was 17.36 ppm (larva I), 19.79 ppm (larva II), 21.69 ppm (larva III), 24.57 ppm (larva IV), 28.78 ppm (pupa), and 11.23 ppm (adult). In the field, a single treatment with C. guianensis flower extract and AuNP (10 × LC50) led to complete larval mortality after 72 h. In standard laboratory conditions, the predation efficiency of golden wonder killifish, Aplocheilus lineatus, against A. stephensi IV instar larvae was 56.38 %, while in an aquatic environment treated with sub-lethal doses of the flower extract or AuNP, predation efficiency was boosted to 83.98 and 98.04 %, respectively. Lastly, the antiplasmodial activity of C. guianensis flower extract and AuNP was evaluated against CQ-resistant (CQ-r) and CQ-sensitive (CQ-s) strains of Plasmodium falciparum. IC50 of C. guianensis flower extract was 43.21 μg/ml (CQ-s) and 51.16 μg/ml (CQ-r). AuNP IC50 was 69.47 μg/ml (CQ-s) and 76.33 μg/ml (CQ-r). Overall, our results showed the multipurpose effectiveness of C. guianensis-synthesized AuNPs, since they may be proposed as newer and safer tools in the fight against CQ-r strains of P. falciparum and for field control of malaria vectors, in synergy with wonder killifish predators