Aegypti Research Articles

High-Throughput Screening System Evaluation of Andrographis paniculata (Burm.f.) Extracts and Their Fractions against Mosquito Vectors.

Infectious diseases that cause illness and/or death in humans can be contracted from mosquito bites. A viable and alternate method of personal protection that can lower the danger of human exposure to mosquito-borne diseases is the use of plant-based repellents. Using a high-throughput screening system, the current work examined the toxicity, contact irritancy, and spatial repellency of Andrographis paniculata crude extract and its fractions against Aedes aegypti, Anopheles minimus, and An. dirus. Five fractions (i.e., F1, F2, F3, F4, and F5) were separated from the crude extract by column and thin layer chromatography and analyzed using high-performance liquid chromatography and mass spectrometry. The major active compounds identified from F3 and F5 were 4-deoxy-11,12-didehydroandrographolide and andrographolide. Three concentrations (1.0, 2.5, and 5.0%) for each of the crude extracts and the five fractions were individually impregnated on nylon netting strips and evaluated against the three mosquito species. Results showed that the highest contact irritancy was elicited by the crude extract at 5% concentration against Ae. aegypti (43.70% escaped). Results of the spatial activity index (SAI) showed that fractions F3 and F5 at 2.5% demonstrated the strongest repellency against Ae. aegypti (SAI = 0.84) and An. minimus (SAI = 0.83), respectively. Both the crude extract and its components did not cause any knockdown or mortality. These findings suggest that fractionation of A. paniculata extracts is valuable in assessing their spatial repellent efficacy against mosquitoes. Fractions F3 and F5 hold promise as natural mosquito repellents and could contribute to developing effective mosquito control strategies.

Evaluation of Larvicidal Properties of Zingiber officinale Rhizome and Allium Sativum Bulbs against Aedes aegypti

This study evaluates the larvicidal potential of methanolic extracts derived from Zingiber officinale (ginger) rhizome and Allium sativum (garlic) bulbs against the 4th instar larvae of Aedes aegypti, a key vector responsible for transmitting diseases such as dengue, yellow fever, chikungunya, and Zika. Due to the increasing resistance of mosquitoes to conventional insecticides, there is a pressing need for alternative, eco-friendly vector control methods. Botanical extracts, known for their pesticidal properties, offer a promising solution. Methanolic extracts were collected from the selected test plant parts and different test solutions were prepared to test their larvicidal efficacy against the fourth instar larvae of Ae. aegypti. The results indicated a significant dose-dependent increase in larval mortality for both extracts. The extracts of Z. officinale consistently showed better larvicidal effects than outperformed the extracts of A. sativum at all tested concentrations, with mortality rates ranging from 14.29% at 62.5 ppm to 79.22% at 500 ppm. In contrast, A. sativum exhibited mortality rates from 11.69% at 62.5 ppm to 76.62% at 500 ppm. The LC50 values further highlighted the greater efficacy of ginger extract, with an LC50 of 219.10 ppm compared to 237.39 ppm for garlic. These results suggest the usage of extracts of ginger rhizomes and garlic bulbs as eco-friendly larvicides against Ae. aegypti mosquitoes.

Kajian Angka Bebas Jentik (ABJ) pada Dataran Tinggi di Kelurahan Kemiling Bandar Lampung

Dengue Fever is caused by the dengue virus transmitted by humans through the bite of Aedes aegypti and Aedes albopictus mosquitoes previously infected with dengue virus from other dengue fever patients. The problem is that there is no vaccine or anti-viral drug for dengue hemorrhagic fever, an extraordinary event of dengue hemorrhagic fever if in the community: someone dies or the mortality rate is fifty percent of the previous one and in one month the number of dengue cases doubles from the previous year. Epidemiological control of the presence of mosquitoes through the 3M movement and the larva-free rate (ABJ) ≥ 95% of the national target. Alternative Fogging is carried out if three or more patients with unexplained fever are found and more than or equal to five percent of larvae are found. Therefore, it is necessary to observe the larval stage of DHF vectors to determine the distribution, mosquito density, the main habitat of larvae, and the alleged risk of transmission. The purpose of this study was to determine the House Index, Container Index, Bruteau Index, Density Figure and ABJ through a larval survey. The sampling technique used proportional random sampling. Research instruments: questionnaires, observation sheets, flashlight equipment to check for the presence of larvae. Results HI, BI and CI Habitat Index > 5%. The larva free rate in Sumberejo Prosperous Village was 87%, indicating a moderate density of potential dengue transmission, because it was below > 95%.

Structural and biological studies on beta – alanine substituted Sulfonamide derivatives: A new class of Juvenile hormone mimics as insect growth regulators

A series of naphthyl-sulfonamide juvenile hormone analogs has been synthesized through one-pot synthesis route using thionyl chloride as an activating agent for carboxylic functional group. The structures of synthesized compounds with general formula C10H7-SO2NH-(CH2)2CON-R1R2 have been confirmed by FT-IR, 1HNMR , 13CNMR , and ESI-MS techniques. The insect growth regulating property of all the synthesized compounds as juvenile hormone analogs (JHAs) has been studied against yellow fever mosquito, Aedes aegypti and tobacco cutworm, Spodoptera litura. The bioassay results demonstrate that the synthesized compounds exhibit insect growth regulating activity in comparison to standard JHAs. The IE50 and IE90 values of B4 are 0.08 and 6.62 ppm, respectively for inhibition of Aedes aegypti and the LC50 and LC90 values of B3 are 11.03 and 45.36 ppm, respectively for Spodoptera litura. Notably, the compounds B3 and B4 showed enhanced efficacy at lower concentrations. Additionally, density functional theory (DFT) technique is used to predict the chemical reactivity and toxicity of the synthesized JHAs in comparison to pyriproxyfen. Further, the DNA-binding study of synthesized JHAs has been carried out using UV–vis spectroscopy for toxicity assessment against DNA and the binding constant values in the range 102 – 103 suggest lower toxicity of all the synthesized molecules in comparison to PYR. All the synthesized JHAs show IGR action and exhibit better reactivity and reduced toxicity as compared to the commercial in use IGRs.

Widespread geographic distribution of Aedes aegypti (Diptera: Culicidae) kdr variants in Panama.

We searched for evidence of knockdown resistance (kdr) mutations in the voltage-gated sodium channel gene of Aedes aegypti (Linnaeus) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) mosquitoes from Panama. Conventional PCR was performed on 469 Ae. aegypti and 349 Ae. albopictus. We did not discover kdr mutations in Ae. albopictus, but 2 nonsynonymous kdr mutations, V1016I (found in 101 mosquitoes) and F1534C (found in 29 of the mosquitoes with the V1016I), were detected in Ae. aegypti. These kdr mutations were present in all specimens that were successfully sequenced for both IIS5-S6 and IIIS6 regions, which included samples collected from 8 of the 10 provinces of Panama. No other kdr mutations were found in Ae. aegypti, including V1016G, which has already been reported in Panama. Findings suggest that the V1016I-F1534C variant is prevalent in Panama, which might be related to the introduction and passive movement of mosquitoes as part of the used-tire trade. However, we cannot rule out the possibility that selection on de novo replacement of kdr mutations also partially explains the widespread distribution pattern of these mutations. These 2 ecological and evolutionary processes are not mutually exclusive, though, as they can occur in tandem. Research in Panama needs to calculate the genotypic and allelic frequencies of kdr alleles in local Ae. aegypti populations and to test whether some combinations confer phenotypic resistance or not. Finally, future studies will have to track the introduction and spreading of new kdr mutations in both Aedes species.

Larval crowding enhances dengue virus loads in Aedes aegypti, a relationship that might increase transmission in urban environments.

Climate change and urbanization will alter the global distribution of disease vectors, changing the disease burden in yet unpredictable ways. Aedes aegypti is a mosquito responsible for transmitting dengue, Zika, chikungunya, and yellow fever viruses that breeds in containers associated with urban environments. We sought to understand how ambient temperature and larval densities in the immature aquatic phases determine adult life history traits and dengue virus loads post-infection. We predicted that larval crowding and high temperatures would both lead to smaller mosquitoes that might struggle to invest in an immune response and, hence, would exhibit high viral loads. We first examined larval densities from urban and rural areas via a meta-analysis. We then used these data to inform a laboratory-based 2x2 design examining the interacting effects of temperature (21 vs. 26°C) and density (0.2 vs. 0.4 larvae/mL) on adult life history and dengue virus loads. We found that urban areas had an ~8-fold increase in larval densities compared to more rural sites. In the lab, we found that crowding had more impact on mosquito traits than temperature. Crowding led to slower development, smaller mosquitoes, less survival, lower fecundity, and higher viral loads, as predicted. The higher temperature led to faster development, reduced fecundity, and lower viral loads. The virus-reducing effect of higher temperature rearing was, however, overwhelmed by the impact of larval crowding when both factors were present. These data reveal complex interactions between the environmental effects experienced by immature mosquitoes and adult traits. They especially highlight the importance of crowding with respect to adult viral loads. Together, these data suggest that urban environments might enhance dengue virus loads and, therefore, possibly transmission, a concerning result given the increasing rates of urbanization globally.

A Native Bacillus Thuringiensis Strain with Higher Insecticidal Activity Against Adult Aedes Aegypti Than the Larvae

Mosquitoes of several species cause the deaths of millions of people annually, making them the major disease vectors. Bioinsecticide formulations derived from Bacillus thuringiensis are widely acknowledged as highly efficient, sustainable, environmentally friendly, and safe means of controlling insect pests. In this study, a strain of B. thuringiensis exhibiting significant efficacy in controlling Aedes aegypti was isolated from the local environment, identified, and physiologically characterized. The isolated B. thuringiensis strain exhibited positive insecticidal activity against the larvae and adult Aedes aegypti, causing mortality of the insect larvae at a rate of 3.33% and adult at 53.33 – 93.33% in 48 hours. Experiments conducted in a controlled laboratory setting showed that B. thuringiensis toxin exhibited higher levels of activity against the adult mosquito than the larvae. This study demonstrates that bioinsecticide formulation using B. thuringiensis as the active agent has the potential to effectively and sustainably manage larvae and adult Aedes aegypti.

Invasive brown algae (Sargassum spp.) as a potential source of biocontrol against Aedes aegypti

Influxes of sargassos are responsible for economic and environmental disasters in areas where they bloom, especially in regions whose main income relies on tourism and with limited capacity for sanitation and public health response. A promising way of valorization would be to convert this incredible biomass into tools to fight the deadly vector mosquito Aedes aegypti. In the present study, we generated hydrolates and aqueous extracts from three main Sargassum morphotypes identified in Guadeloupe (French West Indies): Sargassum natans VIII, Sargassum natans I and Sargassum fluitans. We conducted a chemical characterization and a holistic evaluation of their potential to induce toxic and behavioral effects in Ae. aegypti. Despite the low insecticidal potential observed for all the extracts, we found that S. natans VIII and S. fluitans hydrolates deterred oviposition, induced contact irritancy and stimulated blood feeding behavior in host seeking Ae. aegypti females, while aqueous extracts from S. natans I and S. fluitans deterred both blood feeding behavior and oviposition. Chemical characterization evidenced the presence of phenylpropanoid, polyphenols, amino acids and esters. Thus, Sargassum spp. aqueous extracts and hydrolates could be used to manipulate Ae. aegypti behavior and be valorized as control tools against this mosquito.

Impact of storm drains on the maintenance of dengue endemicity in Presidente Prudente, São Paulo, Brazil: a geospatial and epidemiologic approach.

Dengue is a public health challenge worldwide. Brazil registered about 70% of cases in Latin America in 2023; in 2024, the country is experiencing an unprecedented increase in the number of infected individuals. By May 2024, more than 4 million people were infected. Our goal was to: (1) determine the epidemiology of dengue cases and their spatiotemporal distribution and (2) carry out a survey of the storm drains and through a geospatial analysis to determine their possible correlation with cases of dengue in Presidente Prudente, São Paulo, Brazil. Cases and information on the habitat of mosquito in the storm drain underground drainage system from 2020 to 2021 were obtained from public agencies. Larvae, pupae, and Ae. aegypti were identified according to species and described in taxonomic keys. Kernel density maps were constructed. From 1996 to 2023, the prevalence of cases peaked in 2016 and 2019, and in 2023 reached alarming levels, and the city was considered hyperendemic. In 2021, 2,609 cases were registered with 2 clusters of high density. Of 5,492 storm drains analyzed, 18.0% were found to have water, 9.0% had larvae or pupae of Aedes aegypti and 91.0% were classified as dirty or damaged. A direct correlation between the kernel layer of cases in 2021 with the kernel layer of storm drains containing water (r = 0.651) and larvae and pupae (r = 0.576) was found, suggesting that storm drains are risk factors and have an impact on the maintenance of dengue endemicity. The high number of damaged units found demonstrated the lack of storm drain management, compromising the urban drainage system and possibly contributing to dengue outbreaks. Policymakers may use these findings to improve existing dengue control strategies focusing on the control of storm drains and increase local and global perspectives on reducing dengue outbreaks.

The Effect of a Combination of Ethanol Extract from Leaves and Flowers of Plumeria acuminate L. Against Aedes aegypti Larvae

Aedes aegypti is the primary vector that causes dengue virus (DENV) infection. Ae. aegypti resistance to abate (Temephos) has occurred in Indonesia and several other countries. Innovations are needed to develop alternative ingredients that can be used as natural larvacides. The Plumeria acuminate L. is an Indonesian plant with metabolites that have the potential to act as larvicides. This study aims to determine the potential combination of ethanol extract of P. acuminate L. leaves and flowers as a larvicide for A. aegypti. A laboratory experimental study with a post-test-only control group design was carried out on Ae. aegypti larvae instar III. The larvicide test was carried out according to WHO standards in 2005 with concentrations of 10000, 7500, 5000, and 2500 ppm, as well as control (water and 1% DMSO), with 20 larvae for each concentration. The observation was carried out at the 24th and 48th hours with 3 repetitions. Larval mortality data was analyzed using one-way ANOVA statistical tests to determine significant differences and lethal concentrations (LC50 and LC90) were calculated using probit analysis using SPSS software. The mortality of Ae. aegypti larvae due to the administration of a combined ethanolic extract of P. acuminate L. leaves and flowers was the highest at doses of 10000 and 7500 ppm, which was 100% with lethal concentrations of LC50 and LC90 of 3364.715 and 6293.759 ppm at the 24th hour observation, whereas at the 48th-hour observation, lethal concentrations were detected at 1767.998 and 2941.138 ppm, respectively. One-way ANOVA analysis test showed a significant difference in Ae. aegypti larval mortality due to the administration of a combined ethanol extract of P. acuminate L. leaves and flowers at 24th-hour observation (p = 0.000) and (p = 0.013) at 48th hour observation. The combination of ethanol extract of P. acuminate L. leaves and flowers showed larvicidal activity against Ae. aegypti larvae as evidenced by larvae mortality which were influenced by concentration and observation time.

Chemical constituents and larvicidal activity of the microencapsulated essential oil of Citrus aurantium L. against Aedes aegypti

This study aimed to evaluate the chemical profile and larvicidal activity of the microencapsulated essential oil (EO) of Citrus aurantium L. against Aedes aegypti. The barks of C. aurantium were collected in São Luís-MA. The EO was extracted by hydrodistillation at 100°C for 3h, with chemical characterization through Gas Chromatography coupled with mass spectrometry (GC-MS). Encapsulation of the EO was performed by ionic gelling. To quantify the total phenolic content of the EO, the Folin-Ciocalteu spectrophotometric method was applied. Then, the lethality of the EO against Aedes aegypti was evaluated, and the LC50 for the action of the EO was calculated using the Probit method. The major constituents found in the EO of C. aurantium were: (-)-Terpinen-4-ol (32, 56%) and Caryophyllene oxide (23.52%). The larvicidal activity of the EO showed a LC50 of 3.589 mg L-1. The results indicate that the evaluated EO is composed of substances that provide a good larvicidal effect, revealing its efficiency in combating and controlling Aedes aegypti.

Chemical profile and biotechnological potential larvicidal of a nanoemulsion (o/w) of the essential oil of Salvia officinalis L

This study aims to evaluate the chemical profile and biotechnological larvicidal potential of the nanoemulsion of the essential oil of Salvia officinalis L. The leaves of the plant were collected in São Luís, MA, from January to May 2021. The essential oil was extracted by hydrodistillation at 100°C for 3h. Chemical characterization was obtained by GC-MS. The oil-in-water nanoemulsion was formulated by the low-energy phase inversion method and subjected to thermodynamic stability tests. Antioxidant activity is performed by the spectrophotometric method of scavenging hydroxyl radicals from salicylic acid. For larvicidal activity, Aedes aegypti larvae were subjected to EO solutions and nanoemulsions in concentrations (10-100 mg L-1), larval mortality was evaluated, and the LC50 was determined by the Probit method. The majority compounds of the EO were: eucalyptol with 65.14%, camphor (30.63%), and α-Terpineol (1.53%). The formulations were characterized as nanoemulsions with a droplet size <200 nm. The PDI was <0.200, indicating a narrow size distribution. The antioxidant activity exhibited EC50 of 136.29 mg L-1 and 51.59 mg L-1. The nanoemulsion with larvicidal potential showed an LC50 of 71.17 mg L-1. The nanoemulsion showed bioactive potential for larvicidal action, which may be related to the presence of its chemical compounds, and its use is encouraged in the fight against Aedes aegypti.

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.

Identification and functional analysis of C-type lectin from mosquito Aedes albopictus in response to dengue virus infection

BackgroundC-type lectins (CTLs) are a large family of proteins with sugar-binding activity. CTLs contain an evolutionarily conserved C-type lectin domain (CTLD) that binds microbial carbohydrates in a calcium-dependent manner, thereby playing a key role in both microbial pathogenesis and innate immune responses. Aedes albopictus is an important vector for transmitting dengue virus (DENV) worldwide. Currently, the molecular characteristics and functions of CTLs in Ae. albopictus are largely unknown.MethodsTranscripts encoding CTL proteins in the Ae. albopictus genome assembly were analyzed via sequence blast. Phylogenetic analysis and molecular characterization were performed to identify the functional domains of the CTLs. Quantitative analysis was performed to determine the gene expression features of CTLs during mosquito development and in different tissues of female adults after blood feeding. In addition, the functional role of CTLs in response to DENV infection was investigated in Ae. albopictus mosquito cells.ResultsWe identified 39 transcripts encoding CTL proteins in the Ae. albopictus transcriptome. Aedes albopictus CTLs are classified into three groups based on the number of CTLDs and the domain architecture. These included 29 CTL-Ss (single-CTLDs), 1 immulectins (dual-CTLD) and 9 CTL-Xs (CTLDs with other domains). Phylogenetic analysis and structural modeling indicated that CTLs in Ae. albopictus are highly conserved with the homologous CTLs in Aedes aegypti. The expression profile assay revealed differential expression patterns of CTLs in both developmental stages and in adult female tissues. Knockdown and overexpression of three CTLs (CTL-S12, S17 and S19) confirmed that they can promote dengue virus infection in Ae. albopictus cells.ConclusionsThe CTL genes in Ae. albopictus mosquito and other mosquito species are evolutionarily conserved and exhibit different developmental and tissue expression features. The functional assay indicated that three CTLs in Ae. albopictus mosquitoes are involved in promoting dengue virus infection. Our study revealed that CTLs play important roles in both the physiological processes and viral infection in mosquito vectors.Graphical

Robust mosquito species identification from diverse body and wing images using deep learning

Mosquito-borne diseases are a major global health threat. Traditional morphological or molecular methods for identifying mosquito species often require specialized expertise or expensive laboratory equipment. The use of convolutional neural networks (CNNs) to identify mosquito species based on images may offer a promising alternative, but their practical implementation often remains limited. This study explores the applicability of CNNs in classifying mosquito species. It compares the efficacy of body and wing depictions across three image collection methods: a smartphone, macro-lens attached to a smartphone and a professional stereomicroscope. The study included 796 specimens of four morphologically similar Aedes species, Aedes aegypti, Ae. albopictus, Ae. koreicus and Ae. japonicus japonicus. The findings of this study indicate that CNN models demonstrate superior performance in wing-based classification 87.6% (95% CI: 84.2–91.0) compared to body-based classification 78.9% (95% CI: 77.7–80.0). Nevertheless, there are notable limitations of CNNs as they perform reliably across multiple devices only when trained specifically on those devices, resulting in an average decline of mean accuracy by 14%, even with extensive image augmentation. Additionally, we also estimate the required training data volume for effective classification, noting a reduced requirement for wing-based classification compared to body-based methods. Our study underscores the viability of both body and wing classification methods for mosquito species identification while emphasizing the need to address practical constraints in developing accessible classification systems.Graphical abstract

Larvicidal activity and chemical composition of essential oils against Aedes aegypti Linn (Diptera: Culicidae) and Aedes albopictus Skuse (Diptera: Culicidae)

Introduction Aedes mosquitoes are the main vectors of the dengue, chikungunya, and Zika viruses. Essential oils have been used in research as alternatives to the synthetic insecticides traditionally used in programs to control these diseases. Methods: leaves of plants from the Caatinga biome were used to obtain essential oils which were used for larvicide essays against Aedes aegypti and Aedes albopictus larvae. Results: significant differences were observed in the LC50 values of C. zeylanicum, C. winterianus, E. citriodora, O. micranthum, and T. erecta essential oils in Ae. aegypti, while these differences were observed for A. conyzoides, C. winterianus, E. citriodora, and O. micranthum essential oils in Ae. albopictus, at the analyzed times. The LC50 for 24 h revealed a significant larvicidal effect for all tested samples, with emphasis on the effect of A. conyzoides and L. gracilis essential oils on Ae. aegypti, and the effect of A. conyzoides, C. zeylanicum, C. winterianus, L. gracilis, and O. micranthum essential oils on Ae. albopictus, all with an LC50 &lt; 100 ppm. It was observed a predominance of terpenes as components in the essential oils, and, in some of them, representing the major constituent (citronellal: 47.71% in E. citriodora and 47.63% in C. winterianus; geraniol: 30.54% in C. winterianus; citronellol: 25.61% in E. citriodora; carvacrol: 55.13% in L. gracilis; and cyclohexen-1-one, 2-isopropyl-5-methyl-: 69.94% in T. erecta). The other major compounds observed were precocene (chromene - 97.66% - A. conyzoides), and eugenol (phenylpropanoid - 96.28% and 73.21% - C. zeylanicum and O. micranthum, respectively). Conclusions: the findings of this study revealed the larvicidal potential of these essential oils on Ae. aegypti and Ae. albopictus control, representing an alternative source to the traditional chemical controls used against the populations of these vectors. Further studies on the effects on non-target organisms and the combined action of two or more essential oils evaluated under field conditions are essential for obtaining commercially efficient formulations of these extracts.

Phytochemical analysis and insecticidal effect of essential oils from Myroxylon peruiferum (Leguminosae) and Eugenia gracillima (Myrtaceae) for the control of Aedes aegypti (Diptera: Culicidae)

ABSTRACT The aim of the present study was to evaluate the chemical composition of essential oils from Myroxylon peruiferum and Eugenia gracillima and determine the larvicidal potential of the oils against Aedes aegypti. Essential oils from the leaves and young stems of M. peruiferum (EOLMP and EOAMP) and the leaves of E. gracillima (EOLEG) were obtained through hydrodistillation. The major constituents of EOLMP were α-pinene (18.0%) and δ-cadinene (14.2%); the major constituents of EOAMP were spathulenol (22.9%) and β-elemene (12.4%) and the major constituents of EOLEG were δ-elemene (40.4%) and germacrene D (25.2%). The two oils extracted from M. peruiferum were very active against A. aegypti larvae and had similar lethal concentrations (LC50 = 0.7 mg/mL). The oil extracted from E. gracillima had an LC50 of 1.51 mg/mL. The essential oils from M. peruiferum and E. gracillima constitute promising sources for the formulation of novel insecticides for the control of the mosquito Aedes aegypti.

A pilot field study on Dengue vectors with locally manufactured inexpensive gravid female traps

High prevalence of Aedes aegypti and Ae. albopictus vectors and dengue incidence as well as the presence of the four dengue virus serotypes underscore the need for effective and simple tools to monitor dengue vectors in Sri Lanka. Field studies were therefore undertaken with inexpensive gravid female trap (GFT) fabricated from local materials in Jaffna city in northern Sri Lanka. The study was initiated in April 2022, and GFT-based mosquito collection was conducted from June 2022 to April 2023. Five blocks of 30 to 40 houses, were selected in areas of high dengue prevalence in Jaffna city. Thirty houses were selected within each block and provided with five traps to be placed indoor and outdoor in each house. Conventional larval indices were determined at the beginning, middle and end of the study. Nine rounds of GFT collections were performed to identify and quantify trapped mosquitoes, their parity, and infection with virus serotypes. A total of 2177 and 3069 Aedes were collected respectively in indoor and outdoor GFTs, during nine rounds of collections and identified at the species level where possible. A total of 679 and 433 Ae. aegypti and Ae. albopictus were collected in indoor traps and 377 and 1288 in outdoor traps respectively. Adult and larval indices decreased respectively by 50% and 100% by the end of the study. Parous mosquitoes comprised 93% (of 120) and 94% (of 288) of the collected Ae. aegypti and Ae. albopictus respectively. In 110 pools of female Ae. aegypti and Ae. albopictus screened for virus serotype by PCR, five pools of Ae. aegypti and six pools of Ae. albopictus from both indoor and outdoor collections were positive for DENV-2. GFTs fabricated with locally available and inexpensive materials described here can be effective for monitoring the prevalence of Aedes vector species, parity and dengue virus infection status. The larval indices suggest that the use of GFTs can contribute to reducing dengue transmission.

Evaluation of the Blood Feeding Preference of Aedes aegypti (Diptera: Culicidae) when Offered Diabetic and Non-Diabetic Blood.

Aedes aegypti (L.,1762) is a primary vector of arboviral infections like dengue, yellow fever, Zika. Female mosquitoes are influenced by various physical and chemical cues from host when blood feeding, e.g., they find some individuals with certain blood types or certain conditions more attractive than others. This study determined whether Ae. aegypti shows a preference when offered blood from a patient with diabetes mellitus (DM), an endocrine disorder associated with abnormal glucose metabolism, compared to healthy blood from non-DMs. In the dual feeding experiments, forty newly emerged female mosquitoes were provided with two blood feeding systems with blood from a non-diabetic (healthy) and diabetic patient using artificial feeders. Blood from 12 diabetic and 12 non-diabetic patients was matched by ABO blood type (e.g., diabetic type O blood was compared with non-diabetic type O blood). The number of mosquitoes that landed and fed from each membrane was counted every 2min for thirty minutes. Ae. aegypti species significantly preferred for blood from non-diabetic individuals (50-65% among the different blood type groups) compared to blood from diabetic individuals. Using multiplex allele-specific PCR it was also determined that, Ae. aegypti significantly preferred the O blood group regardless of blood sugar level compared to others. Ae. aegypti has less preference for diabetic blood to non-diabetics. Regardless people affected with this condition need to take preventive measures to reduce mosquito bites as they tend to have weaker immune systems and can experience more severe cases of dengue.

Larvicidal activities of various plant extracted Essential oils against Aedes aegypti (L.) Larvae (Insecta: Diptera: Culicidae)

Larvicidal activities of various plant extracted Essential oils against Aedes aegypti (L.) Larvae (Insecta: Diptera: Culicidae)