Aedes Aegypti Larvae Research Articles

Status Kerentanan Larva Aedes aegypti Terhadap Temephos Di Wilayah Kerja Pelabuhan KKP Kelas II Tarakan

Various methods of vector eradication have been used to overcome the problem of Indonesian dengue fever with the aim of breaking the chain of dengue transmission, one of which is the use of larvicides to eradicate mosquito larvae. The commonly used larvicide is Abate 1G which contains 1% active substance in the form of temephos, but the use of insecticides continuously and in the long term can reduce the killing power of larvicides and resistance can occur more quickly. The aim of this study was to determine the susceptibility status of Aedes aegypti larvae to temephos. This type of research is experimental with post test only control group design. The population in this study were all larvae survey results of larvae in the buffer area of Tarakan City Harbor which will be used as research objects. The samples of this study were initial III and IV instar Aedes aegypti larvae which were the results of raising the first generation (F1) larvae of the survey results. The results showed 80-98% larval mortality at a concentration of 0.02 mg / l at a concentration of 0.02 mg / l with The 24-hour LC50 value was 0.012 mg / l, while the 24-hour LC99 value ranged from 0.035 mg/l. Larvae in the buffer area of the health port office Tarakan were tolerant of temephos and periodic testing should be carried out and if necessary larvicide rotation to avoid resistance

Effect of Curcuma longa rhizome extract and curcumin against laboratory-reared Aedes Aegypti (Diptera: Culicidae) larvae: Alterations of cell ultrastructure and immunoreactivity of octopamine and tyramine in the midgut

Plant bioactive compounds, as an alternative insecticide, play an essential role in mosquito control. The purpose of this study was to evaluate the effect of Curcuma longa rhizome extract and curcumin against Aedes aegypti larvae, focusing on changes in the cell ultrastructure and immunoreactivity of octopamine (OA) and tyramine (TA) in the midgut. The larval bioassay was used following WHO protocols. Ae. Aegypti 3rd – 4th instars larvae collected from the laboratory were exposed to both different concentrations of C. longa rhizome extract and curcumin. Ultrastructural changes in the midgut cells were tested by transmission electron microscope (TEM). OA and TA in the midgut were detected by the immunohistochemical method. At 24 h, curcumin killed 100% of Ae. Aegypti larvae at a concentration of 4 ppm. The LC50 values of curcumin and the rhizome extract were 1.522 and 4.074 ppm respectively. The curcumin caused ultrastructural changes in the larval midgut; damaged cells, epithelial cells microvilli, cell membranes, nucleus, mitochondria, and other cell organelles. Curcumin and the rhizome extract decreased the immunoreactivity of OA and TA in the larval midgut. Curcumin showed significant larvicidal activity against Ae. aegypti larvae mediated by damaged cells and decreased immunoreactivity of OA and TA in the midgut.

CONTAINER DAN RUMAH POSITIF JENTIK NYAMUK AEDES AEGYPTI TERHADAP KEJADIAN DEMAM BERDARAH DENGUE

Dengue Hemorrhagic Fever (DHF) is one of the environmental health problems that tends to increase in the number of sufferers and the wider the area of ??distribution, in line with increasing mobility and population density. In Indonesia, Dengue Hemorrhagic Fever (DHF) has been recognized since 1968 in Surabaya and Jakarta. The presence of Aedes aegypti larvae in an area is an indicator of the presence of Aedes aegypti mosquito populations in that area. Environmental conditions are one of the conditions that can affect the development of mosquito larvae. Based on data from the Toba Samosir District Health Office, the incidence of dengue fever in Toba Samosir Regency continues to increase from year to year. In 2012 there were 24 cases. In 2013 and 2014 it increased to 25 cases and 51 cases. Then in 2015 it increased again to 77 cases. Data in 2016 and 2017 increased sharply to 110 cases and 129 cases. Throughout 2012 to 2017, In January to June 2018 there were 49 cases and Balige District became the highest data contributor. The purpose of this study was to determine the relationship between containers and houses positive for Aedes aegypti mosquito larvae with the incidence of dengue hemorrhagic fever (DHF) in Toba Samosir Regency. Observational study with a case control design with a ratio of 1:1 (49 cases and 49 controls). The statistical test used is Chi-Square. The results of the bivariate analysis showed that the container inside the house was larva positive, the container outside the house was larva positive, and the house was larva positive were risk factors for the incidence of DHF. For this reason, it is necessary to implement PSN in the form of 3M (draining, burying, and planting things).

The use of Annona squamosa leaf as an alternative in the control of Aedes aegypti

Changes in human behavior towards the environment, barriers to urban development, globalization and climate change are some of the factors that contribute to the occurrence and spread of infectious diseases. The incident affects three arboviruses in Brazil, Chikungunya, Dengue and Zika, which are widely disseminated by mosquito vectors distributed throughout the country, related to humans, causing major public health problems. In the absence of effective vaccines and specific treatments, it is important to maintain and integrate ongoing entomological and epidemiological surveillance to guide the country's control and prevention approaches against these arboviroses. The Annonaceae family has been extensively studied to utilize many species as a source of insecticidal compounds with different modes of action on insects. Therefore, this work aimed to develop a natural, economical and sustainable product using Annona squamosa leaf extract as a resource against Aedes aegypti larvae. From the results, one can prove the hypothesis that the natural insecticide developed from the leaf extract of the fruit of the conde (Annona squamosa) is very effective and also effective in reducing the mortality of Aedes aegypti.

TOXICITY OF THE SEED OIL EXTRACTS OF AZADIRACHTA INDICA ON AEDES AEGYPTI LARVAE

A 12 hour toxicity test of the emulsifiable concentrates of the seed oil extract of Azadirachta indica on Aedes aegypti larvae was carried out in the laboratory.The LC50 of the oil extracts used on 280 Aedes aegypti larvae was 5.0ml of the 2.5% seed oil stock solution. Mortality of Aedes aegypti larvae increased with increase in concentration of the oil extract. This value in relation to mortality was significant (p<0.05) as described by the relationship between the concentration of the seed oil extracts and probit mortality, Probit Y = 4.224X + 2.13. Mortality was thus dependent on the concentration of the oil extracts. The seed oil was very toxic on the larvae. The survival of Aedes aegypti larvae in relation to the seed oil extract decreased with increase in time and increased with decrease in concentration

Environmental Factors linked to the Presence of Aedes aegypti Larvae and the Prevalence of Dengue Hemorrhagic Fever

This study aims to examine the effect of climate and the presence of Aedes aegypti larvae on the prevalence of Dengue Hemorrhagic Fever (DHF) in Bukittinggi. In particular, the study was conducted in order to reduce the prevalence of DHF through vector control (Aedes aegypti) guided by the mosquito larvae free rate by proposing a model for environmental management in an Aedes aegypti larva-free area in Bukittinggi. Rainfall, air temperature, and humidity in 2015-2019 in Bukittinggi were measured to analyze their effect on the prevalence of dengue fever. Samples of data on the prevalence of dengue cases were carried out in total population against data on the prevalence of dengue cases, which amounted to 686 cases, and data on mosquito larvae free rates during 2015-2019. By using Pearson correlation analysis, the results show that the average air temperature in Bukittinggi over the last 5 years allows mosquitoes to survive because they have an average air temperature that functions as an optimum breeding vector. High rainfall can be expected to increase the breeding places of the Aedes aegypti so that the population will increase also has an impact on increasing cases in that month and several months later. Furthermore, the results confirm that there is no significant relationship and also no correlation between physical environmental factors, such as air temperature, humidity, and rainfall with the prevalence of dengue cases in Bukittinggi during the 2015-2019 period. Based on the pattern of distribution of DHF cases in Bukittinggi during the 2015-2019 period, controlling the prevalence of DHF cases needs to focus on activities in areas/villages that are endemic for DHF, without neglecting areas/villages where the prevalence of DHF cases is low, both at the temperature of the air and the mosquitoes will cause dengue fever experience optimal development, low, medium, and high rainfall, as well as in humidity where mosquitoes will experience ideal development.

Synthesis, Molecular Structure, Thermal and Spectroscopic Analysis of a Novel Bromochalcone Derivative with Larvicidal Activity

Chalcones belong to the flavonoids family and are natural compounds which show promising larvicidal property against Aedes aegypti larvae. Aiming to obtain a synthetic chalcone derivative with high larvicidal activity, herein, a bromochalcone derivative, namely (E)-3-(4-butylphenyl)-1-(4-bromophenyl)-prop-2-en-1-one (BBP), was designed, synthesized and extensively characterized by 1H- and 13C- nuclear magnetic resonance (NMR), infrared (IR), Raman spectroscopy, mass spectrometry (MS), ultraviolet–visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction. Further, the quantum mechanics calculations implemented at the B3LYP/6–311+G(d)* level of the theory indicate that the supramolecular arrangement was stabilized by C–H⋯O and edge-to-face C–H⋯π interactions. The EGAP calculated (3.97 eV) indicates a good reactivity value compared with other similar chalcone derivatives. Furthermore, the synthesized bromochalcone derivative shows promising larvicidal activity (mortality up to 80% at 57.6 mg·L−1) against Ae. aegypti larvae.

Secondary metabolites produced by solid-state fermentation of a neotropical Aspergillus flavus strain confer anti-mosquito activity with long shelf-life

Fungal metabolites have shown promising potential as alternative tools for controlling mosquito larvae. Here, we evaluated the insecticidal activities of secondary metabolites (smAf) obtained by solid-state fermentation (SSF) of maize substrate inoculated with spores of the fungi Aspergillus flavus and evaluated the smAf toxicity against Aedes aegypti larvae. We further applied computational approaches to predict the interactions of three potential constituents of smAf with the A. aegypti acetylcholinesterases, which consists of a relevant physiological target for insecticides. Our results revealed that esters [Hexadecenoic acid, methyl ester; (E, E) − 9,12-octadecadienoic acid, methyl ester; (E, E) - 11,14-eicosadecanoic acid, methyl ester; (Z, Z) − 9,12-octadecadienoic acid, ethyl ester]; chromene [2,5,5,8a-tetramethyloctahydro-2Hchromene]; fatty acids [Hexadecenoic acid] and aromatic compounds [2-hydroxy-5-methoxybenzaldehyde, propyl ether; 3-hydroxy-4-propionylphenyl acetate; N-(2,4-dimethoxyphenyl) acetamide] were present in smAf. Toxicological bioassays demonstrated that smAf exhibited similar mosquitocidal activities against A. aegypti mosquito larvae just after obtention and after 48 storage months. Our computational predictions revealed the 2,5,5,8a-tetramethyloctahydro-2 H-chromene and acetylcholinesterase as the interaction with the highest binding energy (−7.3 kcal/mol). Our findings reinforce the mosquitocidal potential of smAf and demonstrate its efficacy, even after a long storage period.

Moringa leaf (Moringa oleifera L) flavonoids utilization in suppressing growth of Aedes aegypti larvae

The study was conducted to determine the potential use of Moringa leaf flavonoids as biolarvicides in suppressing the growth of Aedes aegypti mosquito larvae. The design used was a completely randomized design (CRD) with six flavonoid treatments including P0 (0 ppm flavonoids as a negative control), P1 (12.5 ppm flavonoids), P2 (25 ppm flavonoids), P3 (50 ppm flavonoids), P4 ( flavonoids 75 ppm), and P5 (flavonoids 100 ppm). Each treatment was repeated three times. The results of the analysis of diversity (Anova) revealed that Moringa leaf flavonoids had a very significant effect (P = 0.000) on the mortality of A. aegypti mosquito larvae. The administration of 50 ppm flavonoids of Moringa leaf extract caused the mortality of A. aegypti larvae to reach 95%, and at a concentration of 75 ppm, it increased the mortality percentage to 100%. The results of the probit analysis showed that the lethal concentration 50 (LC50) was achieved at a concentration of 7.96 ppm with exposure for 24 hours, while the lethal concentration-time 50 (LT50) at a concentration of 75 ppm was achieved in a shorter time (2.08 hours). Keywords: flavonoids, moringa leaf, Aedes aegypti, biolarvacide

Larvicidal and synergistic potentials of some plant extracts against Aedes aegypti

Introduction: The phytochemical analysis of the methanol extracts of four plants was determined and assayed for their larvicidal activities against the 4th instar larvae of Aedes aegypti, aiming to detect the promising ones. Method: The parts of the plants were sampled, dried out and powdered. The powdery parts of the plants were extracted with the help of methanol at room temperature for 3 days, with agitation. The extract was filtered and concentrated in vacuo. The resulting methanol extracts were tested against the 4th instar larvae of Aedes aegypti. Results: About sixty four percent (64.3%) of the tested extracts had moderate larvicidal activity after 24 hours. The leaf extract of Capsicum annuum was the most active at 1000 ppm. Conclusion: The parts of the plants assayed gave a dissimilar variety of larvicidal potentials, which can be utilized as a control manager for mosquitoes.

New Bioinsecticides From Combination Extract of Leaf and Flower of Breadfruit (Artocarpus Altilis) On Mortality of Aedes Aegypti Larvae

The main vector for the spread of dengue fever is the female mosquito Aedes aegypti. In Indonesia, chemical larvicides are commonly used to control Aedes aegypti larvae. Bioinsecticides made from plants are one option for environmentally friendly larvae control. Leaves and flower of breadfruit Artocarpus altilis contains toxic compound that can function as larvicides. This experimental study used combination of leaf and flower of breadfruit expect that the combination of the two extracs was synergistic and it was more effective in killing Aedes aegypti larvae. The third instar Aedes aegypti larvae was used and divided into control group and test group with concentrations 1000, 2750, 4500, and 6250 ppm and replicated in 3 times with observations every 6, 9, and 24 hours. To identify the significant difference, the mortality data was analyzed using ANOVA and Duncan's test. In probit analysis, LC50 value of breadfruit leaf extract was 1871 ppm with LT50 was 4.2 hours. LC50 value of breadfruit flower extract was 2531 ppm with LT50 was 10.8 hours. LC50 value of the combination of breadfruit leaf and flower extract was 903 ppm with LT50 was 3.7 hours. Based on these studies, it may be indicated that breadfruit leaves and flowers was more effective in killing Aedes aegypti larvae than single extracts

Reversion of CYP450 monooxygenase-mediated acetamiprid larval resistance in dengue fever mosquito, Aedes aegypti L.

Aedes-borne diseases are on the rampant rise despite continued application of chemical insecticide-based interventions. The appearance of high degree of insecticide resistance in Aedes species and noxious effects on environment and non-targets have raised further concerns. Among new chemical interventions, neonicotinoids are considered a safe and effective approach. The present study investigated the control potency of acetamiprid and development of resistance in Aedes aegypti larvae; and the involvement of CYP450 monooxygenases in inducing resistance. The early fourth instars of Ae. aegypti parent susceptible strain (PS) were selected with acetamiprid for 15 generations (ACSF strain) increasing the resistance to 19.74-fold in ACSF-10 and 36.71-fold in ACSF-15. The ACSF-10 larvae were assayed with acetamiprid combined with piperonyl butoxide (PBO) in three different ratios (1:1, 1:5 and 1:10) and selected for next five generations with 1:10 combination. Selection with synergized acetamiprid (APSF strains) reversed as well as reduced the rate of resistance development resulting in only 1.35-fold resistance in APSF-15. The APSF strains showed %monooxygenase dependency ranging from 86.71 to 96.72%. The estimation of the monooxygenases levels in parent and selected larvae showed increased monooxygenase level in the ACSF strains by 2.42-2.87-fold. The APSF-15 strains exhibited 57.95% lower enzyme production than ACSF-15 strain. The reduction and reversion of resistance by using PBO and the elevated levels of monooxygenases in ACSF and reduction in APSF strains recommend the involvement of CYP450-mediated mechanism in the development of acetamiprid resistance in Ae. aegypti. These studies could help in devising resistance management strategies in order to preserve the efficiency of pre-existing insecticides.

Larvicidal Efficacy of Citrus amblycarpa Peel Extract Against the Larvae of Aedes albopictus

Various ways to control dengue vector One of them is by using natural insecticides. The purpose of this study was to test the effectiveness of lime peel powder (Citrus amblycarpa) as an electric mosquito repellent against the death of Aedes albopictus mosquitoes in the field larvae. This study uses a true experimental design conducted at the Tanah Bumbu Health Research and Development Center. The object of this research was lime peel powder (Citrus amblycarpa) which was used as a natural insecticide against the Aedes albopictus mosquito. The larvae used were Aedes aegypti larvae instar III which were hatched at the Research and Development Center of P2B2 Tanah Bumbu and the results of larval collection using ovitrap in the Martapura Health Center Area 1. Susceptibility test for larval mortality and data collection by counting the number of dead Aedes albopictus larvae after being exhibited with skin extract lime for 24 hours at concentrations of 2%, 3%, 4%, and 5%. The LT50 mortality of larvae with lime extract was 2.78 hours (5%), faster than the mortality of larvae in the control group using abate. The results showed the potential of Limau Kuit peel extract as a larvicide in controlling the dengue vector.

Knowledge, Attitudes, and Behavior of Larva Monitoring Interpreter (Jumantik) Cadre as Efforts to Prevent Dengue Cases

Background: Efforts to prevent and control DHF in Palu City are still inadequate. The lack of community participation in the implementation of 3M causes the density of Aedes aegypti larvae to be high.
 Objective: To analyze the knowledge, attitudes and behavior of larva monitoring interpreters before and after being given health education in reducing dengue cases.
 Methods: This type of research is a quasi-experimental, with one group pre and posttest design. Carried out in Palu City, Central Sulawesi Province and Pasang Kayu Regency, West Sulawesi Province. The sample size is 98 Jumantik cadres. The interview study instrument used a set of previously validated and tested questionnaires. Informed consent was taken from all respondents and confidentiality was guaranteed throughout the study. Data were analyzed using SPSS with Paired T-test dependent 
 Results: Knowledge about ways to prevent DHF increased the highest from the pre-test (20.10) post-test (51.77) which means that it increased by 32.3% p = 0.000, the smallest increase in knowledge about the spread of DHF was the pre-test value ( 12.9) post-test (14.2) means an increase of 1.3% p=0.003. The attitude that increased the most was the effort to control DHF with a pre-test value (9.4) post-test (48.2%) increased by 38.8% p = 0.000, while the smallest increase was the attitude of responsibility for controlling DHF with a pre-test value. -test (53.32) post-test (53.50) increased by 0.18% p=0.737. The behavior with the highest increase in value was about larval control with a pre-test score (4.75) post-test (37.78) means an increase of 33.0% p = 0.000, while the smallest increase is the behavior of draining the water tank with the pre-test (26.87) post-test (35.83) increasing 8.96% p = 0.002.
 Conclusion: Health education through counseling methods is effective in increasing the knowledge, attitudes and behavior of Jumantik Cadres in preventing dengue fever in Palu City, Central Sulawesi and Pasangkayu Regency, West Sulawesi

Biosynthesis of copper oxide nanoparticles using Rubia cordifolia bark extract: characterization, antibacterial, antioxidant, larvicidal and photocatalytic activities.

Rubia cordifolia represents the pivotal plant resource belonging to traditional Chinese medicine and Indian Ayurveda. The present study aims to synthesize biocompatible copper oxide nanoparticles (CuONPs) using R. cordifolia bark extracts, characterize the incumbent chemical transitions, and explore their biomedical and environmental applications. The absorbance peak between 250 and 300nm clearly demonstrates the formation of CuONPs in the UV-visible spectrum. Fourier transform infrared spectroscopy results showed the presence of functional groups essential for copper ion reduction. Field emission scanning electron microscopy (FE-SEM) and dynamic light scattering analysis revealed that the CuONPs are spherical-shaped with a mean particle size of 50.72nm. Additionally, the zeta potential demonstrates its robustness at 11.2mV. X-ray diffraction pattern showed mixed phases (Cu, Cu2O, and CuO) of cubic monoclinic crystalline nature. CuONPs exhibited noticeable antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus cereus) pathogenic bacteria. Bacterial cell damages were affirmed through FE-SEM imaging when treated with CuONPs. Further, CuONPs demonstrated considerable antioxidant activities by quenching free radicals such as DPPH (60.75%), ABTs (70.88%), nitric oxide (65.48%) and reducing power (71.44%) in a dose-dependent way. CuONPs showed significant larvicidal activity against Aedes aegypti (65 ± 8.66%), Anopheles stephensi (80 ± 13.69%), and Culex quinquefasciatus (72 ± 13.04%) mosquito larvae. The photocatalytic activity of the CuONPs demonstrates the methylene blue (81.84%) and crystal violet (64.0%) dye degradation potentials, indicating the environmental bioremediation efficacy. Hence the present study is the first report in accounting for the versatile applications of the phyto-CuONPs. Moreover, the green synthesis of CuONPS has future applications in designing the drug for life-threatening diseases and various environmental issues.

Evaluation of the influence of calcium chloride on the behavior of phases of nanosystems applied in the larvicidal control of Aedes aegypti

Systems stabilized by surfactants in order to incorporate different substances at their interfaces, such as hydrophilic polymers and active compounds, are systems capable of establishing vector control of Aedes aegypti. The system was obtained through the surface tension of PPG-5-CETETH-20/calcium chloride dispersion at concentrations of 0.2%, 0.4%, 0.8%, 1% and 2%, determining the CMC of each sample. Then, a binary study was performed and the system structures were evaluated by Polarized Light Microscopy (PLM) and rheological analysis. Biological analysis was performed to assess the mean lethal concentration (LC50) against Aedes aegypti larvae and toxicity to non-target organisms in Artemia salina. In this sense, the objective of this work was to evaluate the influence of calcium chloride on the behavior of phases and on the biological activity of formulations based on the self-aggregation of surfactants, an alternative larval insecticide to be used as a replacement for larval insecticides already on the market.

Uji Efek Larvasida Ekstrak Daun Gamal (Gliricida sepium) terhadap Larva Nyamuk Aedes aegypti

Gamal leaves (Gliricidia sepium) well known as liquid organic fertilizer, are also known to have potential as vegetable larvicides because there are flavonoids, triterpenoids, coumarin, coumaric acid, mitotic acid, and stigmastanol glucoside which can be identified and isolated from various parts from Gamal. The aim of this study was to examine the larvicidal effect of Gamal (G. sepium) leaf extract against larvae of Aedes aegypti mosquitoes. The study was conducted using an experimental design with a posttest-only control group design and a completely randomized design consisting of 6 treatment groups. Two groups as control (positive and negative control), while 4 other groups received treatment of Gamal leaf extract (G. sepium) at doses of 50 ppm (P1), 150 ppm (P2), 250 ppm (P3), and 350 ppm (P4). There was no mortality of larvae Aedes aegypti from pure lines after giving Gamal leaf extract, but mortality only occurred in Aedes aegypti larvae positive control group originating from the field. Unknown LC50 and LC90. A total of 13 (52%) Ae. aegypti strain classified as tolerant, while as many as 19 (76%) larvae of Aedes aegypti originating from the field are classified as resistant.

Formulations of curcumin and d-mannitol as a photolarvicide against Aedes aegypti larvae: Sublethal photolarvicidal action, toxicity, residual evaluation, and small-scale field trial

Dengue, Zika, chikungunya, and yellow fever are arboviruses transmitted by Aedes aegypti mosquito. In this regard, a number of techniques have emerged aiming to combat its proliferation. Elimination of Aedes aegypti larvae by photodynamic action has been reported as an efficient approach. In this regard, this study was aimed at synthetize and characterize formulations with different proportions (w/w) of the plant-based photolarvicidal curcumin and d-mannitol (CCD 1-4) and their evaluation on sublethal photolarvicidal efficiency, photodegradation profile,solubility, internalization, elimination time, persistence in simulated field, growth of microorganisms in water and the toxicity using an animal models (Zebrafish). CCD 3 (curcumin:d-mannitol 50:50 w/w) showed the best efficacy (LC50-24h = 0.01 mg/L), and also presented the shortest internalization and longest elimination time, 60 min and 8 days, respectively. This formulation caused an extrusion into the intestine and peritrophic membrane. Moreover, CCD 3 showed a photodegradation of 50% (in 24 h) under white fluorescent lamps. In a small-scale field trial, CCD 3 had a residual time of 14 days and abnormal microbial growth was not observed. Finally, CCD 3 did not present any toxicity in Zebrafish, after exposition for 24 h at 100 mg/L. Overall, these results raise the possibility of reducing virus transmission through the controlled photoinactivation of Aedes aegypti larvae using a non-toxic plant-based formulated photolarvicide.

Larvicidal activity evaluation of the chemical compounds isolated from n-hexane extract of Derris elliptica root against the Temephos-susceptible strain of Aedes aegypti larvae

Abstract. Sayono S, Anwar R, Sumanto D. 2021. Larvicidal activity evaluation of the chemical compounds isolated from n-hexane extract of Derris elliptica root against the Temephos-susceptible strain of Aedes aegypti larvae. Biodiversitas 23: 757-764. Aedes aegypti is the main vector of Dengue, Chikungunya, and Zika diseases. Temephos resistance of this species has hampered vector control efforts worldwide. Studies proved that Derris elliptica extracts effectively controlled Aedes larvae, so the active compound needed to be isolated. This study evaluated the larvicidal activity of the chemical compounds isolated from n-hexane fractions of Tuba roots against the temephos-susceptible Ae. aegypti larvae. Six isolates were obtained from three of the seven n-hexane fractions. Three levels of concentration of each isolate were formulated for a preliminary bioassay test, and resulted in the two most active compounds, isolates 3 and 6. The final bioassay test results indicated that isolate 3 was more active than isolate 6 with LC50 and LC90 after 24 hours of exposure were 1.607 and 7.399 ppm, and after 48 hours of exposure were 0.926 and 3.206 ppm respectively. Isolate 6 also had high larvicidal activity after 48 hours of exposure, with LC50 and LC90 were 1.056 and 4.647 ppm. Further studies need to be carried out to determine the chemical structures and toxicity mechanisms of the bioactive compounds.

Molecular identification and phylogeny of Steinernema and Heterorhabditis nematodes and their efficacy in controlling the larvae of Aedes aegypti, a major vector of the dengue virus

Aedes aegypti is the mosquito vector of several arboviruses, especially the dengue virus. Aedes aegypti strain resistant to chemical insecticides have been reported worldwide. To tackle this, an entomopathogenic nematode (EPN) may be an alternative bio-control agent. To this end, this study aims to isolate, identify, and analyze the phylogeny of EPNs in Thailand and evaluate their efficacy for controlling the Ae. aegypti larvae. From 12 provinces in Thailand, soil samples were randomly collected, with 118 out of 1,100 them being positive for EPNs (10.73% prevalence) in genera Steinernema (4.46%) and Heterorhabditis (6.27%). Then, molecular discrimination of these two genus was performed based on the sequencing and phylogenetic analysis of the 28S rDNA and internal transcribed spacer regions. The most abundant species of EPN were Heterorhabditis indica, with minor species of Heterorhabditis sp. SGmg3, H. baujardi, S. surkhetense, S. kushidai, S. siamkayai, Steinernema sp. YNd80, Steinernema sp. YNc215, S. guangdongense, and S. huense. The larvicidal activity of five selected EPN isolates were tested against Ae. aegypti. Ten larvae of Ae. aegypti were incubated with different concentration (80, 160, 320, and 640 IJs/larva) of the infective juveniles of EPN in a 24-well and 6-well plates for 4 days. The mortality rates of the larvae were observed daily. Steinernema surkhetense (ePYO8.5_TH) showed the potential to kill mosquito larvae, with the highest mortality rate of 92 ± 9.37% and 89 ± 9.91% after it was treated with 640 IJs/larva in a 24-well plate and 1600 IJs/larva in a 6-well plate, respectively. There is an abundant distribution of EPNs across the country, and S. surkhetense ePYO8.5_TH may be used as a biocontrol agent against Ae. aegypti larvae.