Larvicidal potential of Trachyspermum ammi essential oil and Delphinium speciosum extract against malaria, dengue, and filariasis mosquito vectors.

Mosquito-borne diseases, such as malaria, dengue, and Zika, pose major public health challenges globally, affecting millions of people. The growing resistance of mosquito populations to synthetic insecticides underscores the critical need for effective and environmentally friendly larvicides. Although chemical pesticides can initially be effective, they often lead to negative environmental consequences and health hazards for non-target species, including humans. This study aimed to evaluate the larvicidal effects of Trachyspermum ammi essential oil and Delphinium speciosum extract on the larvae of three major mosquito species: Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Mosquito larvae of Ae. aegypti, An. stephensi, and Cx. quinquefasciatus were reared under controlled laboratory conditions. The larvicidal activity of T. ammi essential oil and D. speciosum extract was evaluated through standard bioassays, using various concentrations of essential oils (10, 20, 40, 80, and 160 ppm) and extracts (160, 320, 640, 1280, and 2560 ppm) to determine the lethal concentration (LC50) values after 24 h of exposure. Fresh plant materials were collected, with the essential oil extracted via hydro-distillation, and the extract prepared using methanol solvent extraction. The chemical composition of T. ammi essential oil was examined using gas chromatography-mass spectrometry (GC-MS). Additionally, the preliminary analysis of the chemical compounds in D. speciosum extract was carried out using thin layer chromatography (TLC) and nuclear magnetic resonance spectroscopy (NMR) techniques. The results indicated that the essential oil of T. ammi exhibited more effective larvicidal activity compared to the D. speciosum extract. Specifically, the essential oil demonstrated LC50 values of 18 ppm for Cx. quinquefasciatus and 19 ppm for Ae. aegypti. In contrast, the D. speciosum extract showed the strongest larvicidal effect against An. stephensi, with an LC50 of 517 ppm. Concentrations of 40 ppm of the essential oil and 1280 ppm of the extract resulted in 100% mortality across all three species. Both the essential oil of T. ammi and the D. speciosum extract exhibited concentration-dependent larvicidal activity, and these results were statistically significant (p < 0.001) compared to the no-treatment group. GC-MS analysis revealed thymol (88.95%), o-cymen-5-ol (4.11%), and γ-terpinene (2.10%) as the major constituents of the T. ammi essential oil. Additionally, TLC verified the presence of alkaloids in both chloroform and methanolic extracts. Proton NMR identified a diterpene structure for these alkaloids. These findings suggest that T. ammi essential oil is a promising candidate for natural mosquito control strategies. Given its efficacy, further research is warranted to explore its potential in integrated vector management programs.

Biocontrol efficacy of cajeput oil against Anopheles stephensi L. mosquito and its effect on non-target species.

Chemical insecticides are effective at controlling mosquito populations, but their excessive use can pollute the environment and harm non-target organisms. Mosquitoes can also develop resistance to these chemicals over time, which makes long-term mosquito control efforts challenging. In this study, we assessed the phytochemical, biochemical, and insecticidal properties of the chemical constituents of cajeput oil. Results show that Melaleuca cajuputi essential oil may exhibit mosquito larvicidal properties against Anopheles stephensi larvae (second-fourth instar) at 24 h post-treatment. At 24 h post-exposure, the essential oil resulted in a significant decrease in detoxifying enzymes. All of these findings indicate that cajeput oil infects An. stephensi larvae directly affect the immune system, leading to decreased immune function. Cajeput oil significantly affects the second, third, and fourth instar larvae of An. stephensi, according to the bioassay results. Cajeput oil does not induce toxicity in non-target Eudrilus eugeniae earthworm species, as indicated by a histological study of earthworms. Phytochemical screening and GC-MS analysis of the essential oil revealed the presence of several major phytochemicals that contribute to mosquito larvicidal activity. The importance of cajeput oil as an effective candidate for biological control of the malarial vector An. stephensi is supported by this study.

Larvicidal activity of green synthesized iron oxide nanoparticles using Grevillea robusta Cunn. leaf extract against vector mosquitoes and their characterization.

Extensive fumigation of synthetic pesticides to control the mosquito vector during each post-monsoon season in Pakistan significantly enhanced the environmental contamination and extinction of beneficial insects from the urban ecosystems. In this context, the present study examined the larvicidal efficacy of green synthesized iron nanoparticles (IONPs), using an aqueous leaf extract of Grevillea robusta against the early 2nd and 4th instar larvae of Aedes aegypti and Anopheles stephensi in Pakistan. The prepared IONPs were characterized by UV-Vis spectrum, FTIR, X-ray diffraction, scanning electron microscopy, and energy-dispersive diffraction. Larvicidal bioassay was conducted at various concentrations (80, 160, 240, 320, and 400 ppm) of IONPs prepared from leaf extract of G. robusta, and readings were taken-every 12 h for two consecutive days. In vitro, larvicidal assay, G. robusta leaf extract IONPs exhibited high mortalities of 64-96% (LC50 = 259.07 ppm; LC90 = 443.92 ppm) for the second instar and 65-98% (LC50 = 238.05 ppm; LC90 = 433.93 ppm) for the fourth instar of Ae. aegypti, while in the case of An. stephensi 56-84% (LC50 = 297.96 ppm; LC90 = 528.69 ppm) for the second and 56-88% (LC50 = 292.72 ppm; LC90 = 514.00 ppm) mortality for fourth larvae at 12-48 h post-exposure times were observed respectively. Significant (p < 0.05) dose-dependent and exposure time-dependent trends were observed among the 2nd and 4th larvalinstar of An. stephensi and Ae. aegypti. However, both species showed similar response and observed no significant (p > 0.05) difference in percentage mortality between the vector mosquitoes An. stephensi and Ae. aegypti. Overall, this study demonstrates that the larvicidal efficacy of green synthesized IONPs at low concentrations can be an ideal eco-friendly and cost-effective biocontrol of vector mosquitoes' larvae of An. stephensi and Ae. aegypti.

Laboratory evaluation of the efficacy of deltamethrin-laced attractive toxic sugar bait formulation on Anopheles stephensi.

BACKGROUND: Attractive toxic sugar bait (ATSB) is a promising "attract and kill"-based approach for mosquito control. It is a combination of flower nectar/fruit juice to attract the mosquitoes, sugar solution to stimulate feeding, and a toxin to kill them. Selecting an effective attractant and optimizing concentration of toxicant is significant in the formulation of ATSB. METHODS: Current study formulated an ATSB using fruit juice, sugar and deltamethrin, a synthetic pyrethroid. It was evaluated against two laboratory strains of Anopheles stephensi. Initial studies evaluated comparative attractiveness of nine different fruit juices to An. stephensi adults. Nine ASBs were prepared by adding fermented juices of plum, guava, sweet lemon, orange, mango, pineapple, muskmelon, papaya, and watermelon with 10% sucrose solution (w/v) in 1:1 ratio. Cage bioassays were conducted to assess relative attraction potential of ASBs based on the number of mosquito landings on each and the most effective ASB was identified. Ten ATSBs were prepared by adding the identified ASB with different deltamethrin concentrations (0.015625-8.0 mg/10 mL) in 1:9 ratio. Each ATSB was assessed for the toxic potential against both the strains of An. stephensi. The data was statistically analysed using PASW (SPSS) software 19.0 program. RESULTS: The cage bioassays with nine ASBs revealed higher efficacy (p < 0.05) of Guava juice-ASB > Plum juice-ASB > Mango juice-ASB in comparison to rest of the six ASB's. The bioassay with these three ASB's ascertained the highest attractancy potential of guava juice-ASB against both the strains of An. stephensi. The ATSB formulations resulted in 5.1-97.9% mortality in Sonepat (NIMR strain) with calculated LC30, LC50, and LC90 values of 0.17 mg deltamethrin/10 mL, 0.61 mg deltamethrin/10 mL, and 13.84 mg deltamethrin/10 mL ATSB, respectively. Whereas, 6.12-86.12% mortality was recorded in the GVD-Delhi (AND strain) with calculated LC30, LC50, and LC90 values of 0.25 mg deltamethrin/10 mL, 0.73 mg deltamethrin/10 mL and 10.22 mg deltamethrin/10 mL ATSB, respectively. CONCLUSION: The ATSB formulated with guava juice-ASB and deltamethrin (0.0015625-0.8%) in 9:1 ratio showed promising results against two laboratory strains of An. stephensi. Field assessment of these formulations is being conducted to estimate their feasibility for use in mosquito control.

Laboratory-based efficacy evaluation of Bacillus thuringiensis var. israelensis and temephos larvicides against larvae of Anopheles stephensi in ethiopia.

BACKGROUND: Malaria, transmitted by the bite of infective female Anopheles mosquitoes, remains a global public health problem. The presence of an invasive Anopheles stephensi, capable of transmitting Plasmodium vivax and Plasmodium falciparum parasites was first reported in Ethiopia in 2016. The ecology of An. stephensi is different from that of Anopheles arabiensis, the primary Ethiopian malaria vector, and this suggests that alternative control strategies may be necessary. Larviciding may be an effective alternative strategy, but there is limited information on the susceptibility of Ethiopian An. stephensi to common larvicides. This study aimed to evaluate the efficacy of temephos and Bacillus thuringiensis var. israelensis (Bti) larvicides against larvae of invasive An. stephensi. METHODS: The diagnostic doses of two larvicides, temephos (0.25 ml/l) and Bti (0.05 mg/l) were tested in the laboratory against the immature stages (late third to early fourth stages larvae) of An. stephensi collected from the field and reared in a bio-secure insectary. Larvae were collected from two sites (Haro Adi and Awash Subuh Kilo). For each site, three hundred larvae were tested against each insecticide (as well as an untreated control), in batches of 25. The data from all replicates were pooled and descriptive statistics prepared. RESULTS: The mortality of larvae exposed to temephos was 100% for both sites. Mortality to Bti was 99.7% at Awash and 100% at Haro Adi site. CONCLUSIONS: Larvae of An. stephensi are susceptible to temephos and Bti larvicides suggesting that larviciding with these insecticides through vector control programmes may be effective against An. stephensi in these localities.

Capsaicin decreases fecundity in the Asian malaria vector Anopheles stephensi by inhibiting the target of rapamycin signaling pathway.

BACKGROUND: Mosquito-borne diseases threaten human health, but mosquito control faces various challenges, such as resistance to chemical insecticides. Thus, there is an urgent need for more effective and environment-friendly control agents. Capsaicin can downregulate the mTOR signaling pathway of tumor cells. The TOR signaling pathway can mediate the expression of vitellogenin (Vg) to regulate the fecundity of insects. Whether capsaicin has the potential to inhibit fecundity of mosquitoes by regulating TOR pathway and Vg expression is currently unclear. METHODS: Anopheles stephensi were fed with blood of mice administered capsaicin by gavage or sugar containing capsaicin followed by a blood feeding with normal mice. Then, the engorged female mosquitoes were tubed individually and underwent oviposition. The eggs and individuals in the subsequent development stages, including larvae, pupae, and emerging adults, were counted and compared between the capsaicin treatment and control groups. Additionally, total RNA and protein were extracted from the engorged mosquitoes at 24 h post blood feeding. Real-time PCR and western blot were performed to detect the transcriptional level and protein expression of the key fecundity-related molecules of mosquitoes. Finally, TOR signaling pathway was inhibited via rapamycin treatment, and changes in fecundity and the key molecule transcription and protein expression levels were examined to verify the role of TOR signaling pathway in the effect of capsaicin on mosquito fecundity. RESULTS: The laid and total eggs (laid eggs plus retained eggs) of An. stephensi were significantly reduced by feeding on the blood of capsaicin-treated mice (P < 0.01) or capsaicin-containing sugar (P < 0.01) compared with those in the control group. Moreover, the transcription and protein expression or phosphorylation levels of fecundity-related molecules, such as Akt, TOR, S6K, and Vg, were significantly decreased by capsaicin treatment. However, the effects disappeared between control group and CAP group after the TOR signaling pathway was inhibited by rapamycin. CONCLUSIONS: Capsaicin can decrease the fecundity of An. stephensi by inhibiting the TOR signaling pathway. These data can help us to not only understand the effect of capsaicin on the reproductive ability of An. stephensi and its underlying mechanism, but also develop new efficient, safe, and pollution-free mosquito vector control agents.

Nanoemulsion and nanogel containing Artemisia dracunculus essential oil; larvicidal effect and antibacterial activity.

OBJECTIVE: Microbial infections and mosquito-borne diseases such as malaria, with 627 k deaths in 2020, are still major public health challenges. RESULTS: This study prepared nanoemulsion and nanogel containing Artemisia dracunculus essential oil. ATR-FTIR analysis (Attenuated Total Reflection-Fourier Transform InfraRed) confirmed the successful loading of the essential oil in nanoemulsion and nanogel. LC50 values (Lethal Concentration 50%) of nanogel and nanoemulsion against Anopheles stephensi larvae were obtained as 6.68 (2-19 µg/mL) and 13.53 (7-25 µg/mL). Besides, the growth of Staphylococcus aureus after treatment with 5000 µg/mL nanogel and nanoemulsion was reduced by ~ 70%. However, about 20% growth of Pseudomonas aeruginosa was reduced at this dose. Considering the proper efficacy of the nanogel as a larvicide and proper antibacterial effect against S. aureus, it could be considered for further investigations against other mosquitoes' larvae and gram-positive bacteria.

Aedes aegypti (L.) and Anopheles stephensi Liston (Diptera: Culicidae) Susceptibility and Response to Different Experimental Formulations of a Sodium Ascorbate Toxic Sugar Bait.

Attractive toxic sugar baits (ATSBs) require target insects to locate, orient toward, and feed on an insecticidal sugar solution to control populations. Formulating these baits with different attractants and phagostimulants can increase their efficacy by causing insects to choose the ATSB over competing natural sugar sources, and to ingest more of the bait solution. We tested formulations of a 20% sodium ascorbate (SA) ATSB solution using different sugars, adenosine triphosphate (ATP), gallic acid, and six plant volatile compounds to determine their effect on adult Aedes aegypti (L.) and Anopheles stephensi Liston mortality. Baits formulated with fructose or sucrose had no effect on either species, neither did the addition of ATP. Gallic acid increased the survival of Ae. aegypti. Four of the six volatile compounds increased mortality in at least one species. We also examined An. stephensi response to baits formulated with each of the six volatile compounds. Anisaldehyde significantly increased the number of mosquitoes responding toward the SA-ATSB, but increasing the amount had no effect. Addition of anisaldehyde also significantly increased An. stephensi feeding rates on the SA-ATSB, though mosquitoes will avoid the toxic bait if a nontoxic sugar source is available. Formulation of SA-ATSBs with synthetic blends of attractive compounds can increase bait efficacy and consistency, though further research is needed to assess their performance in the field in the presence of natural sugar sources.

Mast Cell Chymase/Mcpt4 Suppresses the Host Immune Response to Plasmodium yoelii, Limits Malaria-Associated Disruption of Intestinal Barrier Integrity and Reduces Parasite Transmission to Anopheles stephensi.

An increase in mast cells (MCs) and MCs mediators has been observed in malaria-associated bacteremia, however, the role of these granulocytes in malarial immunity is poorly understood. Herein, we studied the role of mouse MC protease (Mcpt) 4, an ortholog of human MC chymase, in malaria-induced bacteremia using Mcpt4 knockout (Mcpt4-/-) mice and Mcpt4+/+ C57BL/6J controls, and the non-lethal mouse parasite Plasmodium yoelii yoelii 17XNL. Significantly lower parasitemia was observed in Mcpt4-/- mice compared with Mcpt4+/+ controls by day 10 post infection (PI). Although bacterial 16S DNA levels in blood were not different between groups, increased intestinal permeability to FITC-dextran and altered ileal adherens junction E-cadherin were observed in Mcpt4-/- mice. Relative to infected Mcpt4+/+ mice, ileal MC accumulation in Mcpt4-/- mice occurred two days earlier and IgE levels were higher by days 8-10 PI. Increased levels of circulating myeloperoxidase were observed at 6 and 10 days PI in Mcpt4+/+ but not Mcpt4-/- mice, affirming a role for neutrophil activation that was not predictive of parasitemia or bacterial 16S copies in blood. In contrast, early increased plasma levels of TNF-α, IL-12p40 and IL-3 were observed in Mcpt4-/- mice, while levels of IL-2, IL-10 and MIP1ß (CCL4) were increased over the same period in Mcpt4+/+ mice, suggesting that the host response to infection was skewed toward a type-1 immune response in Mcpt4-/- mice and type-2 response in Mcpt4+/+ mice. Spearman analysis revealed an early (day 4 PI) correlation of Mcpt4-/- parasitemia with TNF-α and IFN-γ, inflammatory cytokines known for their roles in pathogen clearance, a pattern that was observed in Mcpt4+/+ mice much later (day 10 PI). Transmission success of P. y. yoelii 17XNL to Anopheles stephensi was significantly higher from infected Mcpt4-/- mice compared with infected Mcpt4+/+ mice, suggesting that Mcpt4 also impacts transmissibility of sexual stage parasites. Together, these results suggest that early MCs activation and release of Mcpt4 suppresses the host immune response to P. y. yoelii 17XNL, perhaps via degradation of TNF-α and promotion of a type-2 immune response that concordantly protects epithelial barrier integrity, while limiting the systemic response to bacteremia and parasite transmissibility.

Evaluation of anti-malaria potency of wild and genetically modified Enterobacter cloacae expressing effector proteins in Anopheles stephensi.

BACKGROUND: Malaria is one of the most lethal infectious diseases in tropical and subtropical areas of the world. Paratransgenesis using symbiotic bacteria offers a sustainable and environmentally friendly strategy to combat this disease. In the study reported here, we evaluated the disruption of malaria transmission in the Anopheles stephensi-Plasmodium berghei assemblage using the wild-type (WT) and three modified strains of the insect gut bacterium, Enterobacter cloacae. METHODS: The assay was carried out using the E. cloacae dissolvens WT and three engineered strains (expressing green fluorescent protein-defensin (GFP-D), scorpine-HasA (S-HasA) and HasA only, respectively). Cotton wool soaked in a solution of 5% (wt/vol) fructose + red dye (1/50 ml) laced with one of the bacterial strains (1 × 109cells/ml) was placed overnight in cages containing female An. stephensi mosquitoes (age: 3-5 days). Each group of sugar-fed mosquitoes was then starved for 4-6 h, following which time they were allowed to blood-feed on P. berghei-infected mice for 20 min in the dark at 17-20 °C. The blood-fed mosquitoes were kept at 19 ± 1 °C and 80 ± 5% relative humidity, and parasite infection was measured by midgut dissection and oocyst counting 10 days post-infection (dpi). RESULTS: Exposure to both WT and genetically modified E. cloacae dissolvens strains significantly (P < 0.0001) disrupted P. berghei development in the midgut of An. stephensi, in comparison with the control group. The mean parasite inhibition of E. cloacaeWT, E. cloacaeHasA, E. cloacaeS-HasA and E. cloacaeGFP-D was measured as 72, 86, 92.5 and 92.8 respectively. CONCLUSIONS: The WT and modified strains of E. cloacae have the potential to abolish oocyst development by providing a physical barrier or through the excretion of intrinsic effector molecules. These findings reinforce the case for the use of either WT or genetically modified strains of E. cloacae bacteria as a powerful tool to combat malaria.

Preparation and Optimization of Peppermint (Mentha pipertia) Essential Oil Nanoemulsion with Effective Herbal Larvicidal, Pupicidal, and Ovicidal Activity against Anopheles stephensi.

OBJECTIVES: The Plasmodium parasite is transmitted directly to humans through the Anopheles mosquito bite and causes vector-borne malaria, leading to the transmission of the disease in Southeast Asia, including India. The problem of persistent toxicity, along with the growing incidence of insect resistance, has led to the use of green pesticides to control the spread of the disease in a cost-effective and environment-friendly manner. Based on this objective, this work investigated the larvicidal, pupicidal, and ovicidal activity of Mentha pipertia using a natural nanoemulsion technique. METHODS: GC-MS characterized essential oils of Mentha pipertia leaves were formulated as a nanoemulsion for herbal larvicidal, pupicidal, and ovicidal activities. Size of the nanoemulsion was analyzed by photon correlation spectroscopy. The herbal activities against Anopheles Stephensi of nanoemulsion were evaluated in terms of the lethal concentration for 50% (LC50) and 90% (LC90) to prove low cost, pollution free active effective formulation. RESULTS: Chiral, keto, and alcohol groups are obtained from Mentha pipertia leaves' essential oil, and the nanoemulsions have demonstrated good results in the larvicidal probit analysis, with values of LC50=09.67 ppm and LC90=20.60 ppm. Activity results of the most stable nano formulation with 9.89 nm size showed a significant increase when compared to the bulk. CONCLUSION: The nanoemulsion of Mentha pipertia leaves can be a promising eco-friendly widely available, low-cost herbicide against the Anopheles mosquito.

Preparation of nanoemulsion of Cinnamomum zeylanicum oil and evaluation of its larvicidal activity against a main malaria vector Anopheles stephensi.

PURPOSE: There is a growing need to use green and efficient larvicidal as alternatives for conventional chemicals in vector control programs. Nanotechnology has provided a promising approach for research and development of new larvicides. Larvicidal potential of a nanoemulsion of Cinnamomum zeylanicum essential oil reports against Anopheles stephensi. METHODS: The nanoemulsion of was formulated in various ratios comprising of C. zeylanicum oil, tween 80, span 20 and water by stirrer. It was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). All components of C. zeylanicum essential oil were identified by GC-MS analysis. The larvicidal potential of the oil and its nanoformulation were evaluated against larvae of An. stephensi. The stability and durability of nanoemulsion was observed over a period of time. RESULTS: Sixty one components in the oil were identified, cinnamaldehyde (56.803%) was the main component. The LC90 and LC50 values of C. zeylanicum essential oil were calculated as 49 ppm and 37 ppm, respectively. The nanoemulsion droplets were found spherical in shape. It was able to kill 100% of larvae in up to 3 days. It was stable after dilution and increased its larvicidal activity up to 32% compared with the essential oil. CONCLUSIONS: A novel larvicide based on nanotechnology introduced. This experiment clearly showed increasing larvicidal activity and residual effect of the nanoformulation in comparison with the bulk essential oil. It could be concluded that this nanoemulsion may be considered as safe larvicide and should be subject of more research in this field.

Solid-lipid nanoparticles (SLN)s containing Zataria multiflora essential oil with no-cytotoxicity and potent repellent activity against Anopheles stephensi.

Malaria is still a global health concern with more than 400,000 death annually. Personal protection using mosquitoes' repellent is an effective prevention strategy, especially in endemic areas. The toxic effects of synthetics repellents and their adverse effects on fabricated goods have made the development of green repellent critical. In this study, ingredients of Zataria multiflora essential oil (ZMEO) were identified using GC-MS analysis. Solid-lipid nanoparticles containing ZMEO (1%) were prepared (SLN-ZMEO) using the high-pressure homogenizer method. The repellent activity of ZMEO and SLN-ZMEO was investigated using Klun and Debboun method and compared together. Besides, their cytotoxicity on a human skin normal cell line (HFFF2) was evaluated. Five major components of ZMEO were carvacrol (27.05%), thymol (26.452%), γ-terpinene (15.144%), o-cymene (13.584%), and α-pinene (9.483%). The SLN-ZMEO showed a spherical shape with a particle size of 134 ± 7 nm. Moreover, their polydispersity index (PDI), zeta potential and entrapment efficiency were determined as 0.24 ± 0.1, - 9.82 ± 0.95 mV and 64.6 ± 3.8%, respectively. Interestingly, the protection time of nanoformulation (93 ± 5 min) was three times longer than that of the non-formulated essential oil (29 ± 2 min). Interestingly, both samples did not show cytotoxicity on HFFF2. Therefore, the prepared nanoformulation can be used as a green and potent repellent.

Preparation of a Nanoemulsion of Essential Oil of Acroptilon repens Plant and Evaluation of Its Larvicidal Activity agianst Malaria Vector, Anopheles stephensi.

Background: Extensive use of chemical larvicides to control larvae, has led to resistance in vectors. More efforts have been conducted the use of natural products such as plant essential oils and their new formulations against disease vectors. Nanoformulation techniques are expected to reduce volatility and increase larvicidal efficacy of essential oils. In this study for the first time, a larvicide nanoemulsion from the essential oil of Acroptilon repens was developed and evaluated against Anopheles stephensi larvae under laboratory conditions. Methods: Fresh samples of A. repens plant were collected from Urmia, West Azarbaijan Province, Iran. A clevenger type apparatus was used for extracting oil. Components of A. repens essential oil (AEO) were identified by gas chromatography-mass spectrometry (GC-MS). All larvicidal bioassay tests were performed according to the method recommended by the World Health Organization under laboratory condition. Particle size and the morphologies of all prepared nanoformulations determined by DLS and TEM analysis. Results: A total of 111 compounds were identified in plant. The LC50 and LC90 values of AEO calculated as 7 ppm and 35 ppm respectively. AEO was able to kill 100% of the larvae in 4 days. Conclusion: The nanoemulsion of AEO showed a weak effect on the larvar mortality. It may therefore be suggested that this kind of nanoemulsion is not appropriate for the formulation as a larvicide. It is important to screen native plant natural products, search for new materials and prepare new formulations to develop alternative interventions with a long-lasting impact.

Evaluation of Nanoemulsion of Eucalyptus globulus Oil as Potent Botanical Larvicide against Malaria Vector, Anopheles stephensi and West Nile Vector, Culex pipiens Under Laboratory and Semi-Field Conditions.

Background: Due to undesired environmental impact of insecticides as well as resistant of vectors to them, the development of organic and natural insecticides has been more considered. In the current study, we developed nanoemulsion of eucalyptus and investigated lavicidal activity of it against malaria vector, Anopheles stephensi and Culex pipiens under laboratory as well as semi-field conditions. Methods: An optimized nanoemulsion was prepared by mixing Eucalyptus oil, Tween 80 and ethanol at ratio of 1:2:1.5 in distilled water, then, stirred for 20 minutes at room temperature. The product was then used for bioassay tests against 3-4th instar larvae of Anopheles stephensi as well as Culex pipiens. Furthermore, a semi-field trial was carried out to evaluate larvicidal activity of nanoemulsion of eucalyptus. Results: Nanoemulsion of eucalyptus showed significantly high lavicidal activity comparing with bulk eucalyptus essential oil. The LC50 and LC90 value of nanoemulsion against An. stephensi were 111.0 and 180.8 ppm respectively and 29.5 and 73.7 ppm for Cx. pipiens, respectively. In the semi field condition, the Nanoemulsion of eucalyptus decreased 1-2nd instar larval density of Culicines and Anophelines to 90.1% and 85.2%, respectively. Conclusion: The nano formulation of eucalyptus oil showed high larvicidal activity. Therefore, nanoemulsion of eucalyptus oil can be used as an eco-friendly larvicide against mosquitoes.

Evaluation of the larvicidal potential of root and leaf extracts of Saussurea costus (Falc. ) Lipsch. against three mosquito vectors: Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus

Abstract INTRODUCTION: The larvicidal potential of Saussurea costus (Falc.) Lipsch. was studied against the early 4th instar larvae of Anopheles stephensi Liston., Aedes aegypti Linn.,and Culex quinquefasciatus Say. because of the emergence of mosquito resistance to conventional synthetic insecticides. METHODS: At concentrations of 12.5-200 ppm, larvicidal activities were studied under laboratory conditions. RESULTS: After 24 h of exposure, the methanol extract of the roots recorded the highest larvicidal activity against An. stephensi, with LC50 and LC90values of 7.96 and 34.39 ppm, respectively. CONCLUSIONS: We are developing potent larvicidal compound(s) from S. costus for controlling the mosquito larval population.

Chemical composition and larvicidal activities of essential oil of Cinnamomum camphora (L. ) leaf against Anopheles stephensi

Abstract INTRODUCTION Anopheles stephensi is the main malaria vector in Southeast Asia. Recently, plant-sourced larvicides are attracting great interests. METHODS: The essential oil was extracted from the leaf of Cinnamomum camphora (L.), and a bioassay was conducted to determine the larvicidal efficacy. The chemical composition of the essential oil was determined by GC-MS analysis. RESULTS: The oil showed strong, dose-dependent larvicidal activities. The onset of larvicidal efficiency was rapid. The LC50 and LC95 were determined as 0.146% and 1.057% at 1 h, 0.031% and 0.237% at 12 h, 0.026% and 0.128% at 24 h, respectively. The oil contains 32 compounds. CONCLUSIONS The essential oil of C. camphora leaf has an excellent larvicidal potential for the control of A. stephensi.

Essential Oil Composition and Larvicidal Evaluation of Platycladus orientalis against Two Mosquito Vectors, Anopheles stephensi and Culex pipiens.

BACKGROUND: Natural plant products as larvicides could be considered as desirable alternatives to synthetic chemical insecticides for vector management. This study was undertaken to assess the mosquito larvicide activity of the essential oil from fresh leaves of Platycladus orientalis against two medically important species of mosquito vectors. METHODS: Essential oil was extracted by hydrodistillation and analyzed with gas chromatography and mass spectrometry (GC-MS). Fresh leaves of P. orientalis tree (500g) were collected in June 2014 from Tehran, Iran and was authenticated at the Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.In addition, the larvicidal potential of oil was evaluated against late-3rd or young-4th instar larvae of Anopheles stephensi and Culex pipiens under laboratory condition. The mortality counts were made after 24h and LC50 and LC90 values were calculated. RESULTS: Forty-six components in leaves of P. orientalis were identified. The major components were α-Pinene (20.17%), 3-Carene (14%) and Cedrol (9.51%). The LC50 values against An. stephensi and Cx. pipiens larvae were 11.67ppm and 18.60ppm after 24h, respectively. CONCLUSION: Platycladus orientalis oil could be considered as a natural larvicide for mosquito larval control.

Larvicidal Activity of Bunium persicum Essential Oil and Extract against Malaria Vector, Anopheles stephensi.

BACKGROUND: Malaria, a mosquito-transmitted disease, is still a major human health problem all over the world. Larviciding is a component of comprehensive control program to overcome the disease. Negative aspects of synthetic insecticides application, such as environmental safety concerns, have favored use of natural insecticides. METHODS: Larvicidal activity of essential oil, extracts and fractions of a wild grown and a cultivated type of Bunium persicum fruits against malaria vector Anopheles stephensi was assessed according to the method described by WHO. RESULTS: Bunium persicum showed remarkable potency against An. stephensi larvae. LC 50 values for essential oil, total extract, petroleum ether fraction and methanol fraction were 27.4284, 64.9933, 85.9933 and 255.7486ppm for wild type, and 21.3823, 63.2580, 62.7814 and 152.6357ppm for cultivated one. CONCLUSION: The results of this study suggest B. persicum as a valuable source of natural insecticides against malaria vector Anopheles stephensi.

Nanoemulsion of Dill essential oil as a green and potent larvicide against Anopheles stephensi.

Indiscriminate use of industrial larvicides causes environment pollution and resistance against the larvicides in mosquitoes. Essential oils (EOs) have many biological activities such as larvicidal effects which have been proposed as new alternatives for industrial ones. Many components of EOs are volatile, thus, should be formulated to retain their activity. Components of Dill EO were identified by GC-MS analysis. Larvicidal activity (LA) of bulk Dill EO (non-formulated) was evaluated against Anopheles stephensi in line with WHO guideline for lab tests. For the first time, nanoemulsions of Dill EO were prepared. Various nanoemulsions having fixed amounts of Dill EO 1.2%, comparable with lethal concentration (LC) at 90% of bulk Dill EO, were prepared having tween 20 (5-30%) with/out ethanol (5-30%). LA of two selected nanoemulsions were then evaluated and compared with that of bulk Dill EO. Five ingredients of oil, with high amounts, were identified as p-Cymenealpha (20.81%), alpha-Phellandrene (20.75%), Carvone (10.97%), Dill ether (9.88%), and cis-Sabinol (3.61%). LC of Dill EO at 50 and 90% were found as 38.8 and 65 ppm, respectively, against 3rd and 4th instar larvae of An. stephensi (Beech-Lab strain). Particle size (PS) ranges of nanoemulsions were 10.7-1880.0 nm. LA of optimum nanoemulsion (PS: 10.7 nm) was significantly better than that of bulk Dill EO. The preparation showed stability against 200 times dilution during larvicidal tests and performed significantly better than the nanoemulsion which was not stable after dilution. To obtain improved efficiency against larvae using nanoemulsions of EOs, the nanoemulsion should be resistant against dilution. Such a stable and green nanoemulsion may be used as alternative to industrial larvicides.