Aegypti Research Articles

Altered thermal preferences of infected or immune-challenged Aedes aegypti and Aedes japonicus mosquitoes

Temperature is a critical factor shaping physiology, life cycle, and behaviour of ectothermic vector insects, as well as the development and multiplication of pathogens within them. However, the influence of pathogen infections on thermal preferences (behavioural thermoregulation) is not well-understood. The present study examined the thermal preferences of mosquitoes (Aedes aegypti and Ae. japonicus) infected with either Sindbis virus (SINV) or Dirofilaria immitis over 12 days post exposure (p.e.) or injected with a non-pathogenic Sephadex bead over 24 h in a thermal gradient (15–30 °C). SINV-infected Ae. aegypti preferred 5 °C warmer temperatures than non-infected ones at day 6 p.e., probably the time of highest innate immune response. In contrast, D. immitis-infected Ae. japonicus preferred 4 °C cooler temperatures than non-infected ones at day 9 p.e., presumably a stress response during the migration of third instar larvae from their development site to the proboscis. Sephadex bead injection also induced a cold preference in the mosquitoes but to a level that did not differ from control-injections. The cold preference thus might be a strategy to escape the risk of desiccation caused by the wound created by piercing the thorax. Further research is needed to uncover the genetic and physiological mechanisms underlying these behaviours.

Chemical Composition, Repellent, and Oviposition Deterrent Potential of Wild Plant Essential Oils against Three Mosquito Species.

In this study, the chemical composition, repellent, and oviposition deterrent effects of five plant essential oils (EOs) extracted from Lantana camara (Verbenaceae), Schinus terebinthifolia (Anacardiaceae), Callistemon viminalis (Myrtaceae), Helichrysum odoratissimum (Asteraceae), and Hyptis suaveolens (Lamiaceae) were evaluated against Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus. When tested at 33.3 µg/cm2, L. camara, S. terebinthifolia, C. viminalis, and H. odoratissimum were effective repellents against Ae. aegypti (89%, 91%, 90%, and 51% repellency, respectively), but they were less repellent against An. gambiae (66%, 86%, 59%, and 49% repellency, respectively). Interestingly, L. camara, S. terebinthifolia, C. viminalis, and H. odoratissimum exhibited 100% repellency against Cx. quinquefasciatus at 33.3 μg/cm2. In time-span bioassays performed at 333 μg/cm2, the EO of L. camara exhibited 100% repellence against Ae. aegypti and An. gambiae for up to 15 min and against Cx. quinquefasciatus for 75 min. The oviposition bioassays revealed that L. camara exhibited the highest activity, showing 85%, 59%, and 89% oviposition deterrence against Ae. aegypti, An. gambiae, and Cx. quinquefasciatus, respectively. The major compounds of L. camara, S. terebinthifolia, and C. viminalis were trans-β-caryophyllene (16.7%), α-pinene (15.5%), and 1,8-cineole (38.1%), respectively. In conclusion, the L. camara and S. terebinthifolia EOs have the potential to be natural mosquito repellents.

The Relationship of Clean and Healthy School Living Behavior and the Incidence of Dengue Fever in Students of SMPN 1 Pancur Batu, Deli Serdang

Dengue hemorrhagic fever is a disease caused by the dengue virus and spread by the Aedes Aegypti mosquito. DHF cases in Indonesia in 2022 will continue to increase by 131,265 cases, while in North Sumatra in 2022 they will increase by 2,923 cases and in Deli Serdang Regency in 2022 they will increase by 803 cases. Poor PHBS (Clean and Healthy Living Behavior) is one of the causes of dengue fever transmission. The aim of this research was to determine the relationship between PHBS and the incidence of dengue fever in students at SMPN 1 Pancur Batu, Deli Serdang. This research is quantitative research with a questionnaire instrument and uses the Chi Square Test method. The population of this study were all students of SMPN 1 Pancur Batu, Deli Serdang with a sample of 85 respondents. The research results show the characteristics of respondents in terms of gender with the majority being 50 respondents (58.8%) women and 35 men (41.2%). In the behavior variable of washing hands using running water at school, the p value = 0.222, the behavior of eradicating mosquito larvae at school has a p value = 0.006, the behavior of throwing away rubbish at school has a p value = 0.001, and the behavior of cleaning the bathtub at school has a p value. = 0.000. Concluded and the variables that were related to the incidence of dengue fever were the behavior variable for eradicating mosquito larvae at school, the behavior variable for throwing away rubbish at school, and the behavior variable for cleaning bathtubs at school.

Entomological surveys and insecticide susceptibility profile of Aedes aegypti during the dengue outbreak in Sao Tome and Principe in 2022.

The first dengue outbreak in Sao Tome and Principe was reported in 2022. Entomological investigations were undertaken to establish the typology of Aedes larval habitats, the distribution of Ae. aegypti and Ae. albopictus, the related entomological risk and the susceptibility profile of Ae. aegypti to insecticides, to provide evidence to inform the outbreak response. Entomological surveys were performed in all seven health districts of Sao Tome and Principe during the dry and rainy seasons in 2022. WHO tube and synergist assays using piperonyl butoxide (PBO) and diethyl maleate (DEM) were carried out, together with genotyping of F1534C/V1016I/V410L mutations in Ae. aegypti. Aedes aegypti and Ae. albopictus were found in all seven health districts of the country with high abundance of Ae. aegypti in the most urbanised district, Agua Grande. Both Aedes species bred mainly in used tyres, discarded tanks and water storage containers. In both survey periods, the Breteau (BI > 50), house (HI > 35%) and container (CI > 20%) indices were higher than the thresholds established by WHO to indicate high potential risk of dengue transmission. The Ae. aegypti sampled were susceptible to all insecticides tested except dichlorodiphenyltrichloroethane (DDT) (9.2% mortality, resistant), bendiocarb (61.4% mortality, resistant) and alpha-cypermethrin (97% mortality, probable resistant). A full recovery was observed in Ae. aegypti resistant to bendiocarb after pre-exposure to synergist PBO. Only one Ae. aegypti specimen was found carrying F1534C mutation. These findings revealed a high potential risk for dengue transmission throughout the year, with the bulk of larval breeding occurring in used tyres, water storage and discarded containers. Most of the insecticides tested remain effective to control Aedes vectors in Sao Tome, except DDT and bendiocarb. These data underline the importance of raising community awareness and implementing routine dengue vector control strategies to prevent further outbreaks in Sao Tome and Principe, and elsewhere in the subregion.

Role of miRNAs in the Chikungunya virus replication and pathogenesis

Chikungunya virus (CHIKV) is a vector-born alphavirus responsible for chikungunya fever with clinical manifestation of polyarthritis transmitted by Aedes aegypti and Aedes albopictus. Establishing viral pathogenesis needs host machinery modulation, and the microRNAs (miRNA) modulate host cellular machinery to establish the infection or inhibit viral replication. miRNAs are the small noncoding RNA that control the gene expression. They are essential in cell differentiation, growth, development, and apoptosis. It also affects disease progression, cancer, and viral infection. CHIKV infection causes differential expression of miRNA, and miRNA has target genes involved in different cellular functions. These target genes may be crucial in CHIKV replication and cell growth. Suppression or overexpression of these miRNAs may have been linked with CHIKV pathogenesis by regulating immune and signaling pathways. Identification of biomarkers in disease progression through the study of circulating miRNAs during CHIKV infection is an emerging field. Therefore, understanding miRNAs’ differential expression and function during CHIKV infection is essential. The detailed studies on the miRNA-mediated regulatory network will provide new ways to develop miRNA-based therapies.

Automatic mapping of high-risk urban areas for Aedes aegypti infestation based on building facade image analysis.

Dengue, Zika, and chikungunya, whose viruses are transmitted mainly by Aedes aegypti, significantly impact human health worldwide. Despite the recent development of promising vaccines against the dengue virus, controlling these arbovirus diseases still depends on mosquito surveillance and control. Nonetheless, several studies have shown that these measures are not sufficiently effective or ineffective. Identifying higher-risk areas in a municipality and directing control efforts towards them could improve it. One tool for this is the premise condition index (PCI); however, its measure requires visiting all buildings. We propose a novel approach capable of predicting the PCI based on facade street-level images, which we call PCINet. Our study was conducted in Campinas, a one million-inhabitant city in São Paulo, Brazil. We surveyed 200 blocks, visited their buildings, and measured the three traditional PCI components (building and backyard conditions and shading), the facade conditions (taking pictures of them), and other characteristics. We trained a deep neural network with the pictures taken, creating a computational model that can predict buildings' conditions based on the view of their facades. We evaluated PCINet in a scenario emulating a real large-scale situation, where the model could be deployed to automatically monitor four regions of Campinas to identify risk areas. PCINet produced reasonable results in differentiating the facade condition into three levels, and it is a scalable strategy to triage large areas. The entire process can be automated through data collection from facade data sources and inferences through PCINet. The facade conditions correlated highly with the building and backyard conditions and reasonably well with shading and backyard conditions. The use of street-level images and PCINet could help to optimize Ae. aegypti surveillance and control, reducing the number of in-person visits necessary to identify buildings, blocks, and neighborhoods at higher risk from mosquito and arbovirus diseases.

Development and validation of a PCR-based method to differentiate human sex in blood-fed Aedes aegypti (Diptera: Culicidae).

Monitoring mosquito host choice to identify high-risk groups for different vector-borne diseases is important to devise vector control strategies and disease management. The present study was conducted to develop and validate a PCR-based method to identify human sex in blood-fed Aedes aegypti mosquitoes. Several human genes present in both the X and Y chromosomes were screened and diagnostic PCR primers were successfully designed and amplified for the human STS gene. The limit of detection of this PCR assay was carried out on Ae. aegypti fed with human blood up to 5 days (120 hours) post blood-meal under laboratory condition. The efficiency of this PCR assay was evaluated in field-collected Ae. aegypti mosquitoes and compared with other existing methods. The developed PCR primers can successfully amplify and distinguish human sex in mosquitoes up to 72 hours after a blood meal, with an amplified product of 627bp and 298bp for male (XY) and 627bp for female (XX) blood-fed mosquitoes. Further, validation of this assay in field-collected Ae. aegypti mosquitoes revealed that this assay could detect human sex in mosquito blood meal substantially more efficiently (c2 = 4.5, p = 0.034) than other PCR based assay. The newly developed PCR assay highly specific to human DNA and can distinguish male and female DNA for up to 72 hours. This assay can be is used for identifying highrisk groups and extended to other medically important hematophagous insects to assess their role in disease transmission and epidemic preparedness.

‘Seven Plus One’ a unique approach to assess the knowledge, attitude and practices for dengue prevention and control among frontline workers of a teaching institution in Rishikesh, Uttarakhand

ABSTRACT Background: Dengue which is an arboviral disease transmitted by Aedes aegypti mosquito, drastically affected communities worldwide. It has been showing consistently a rising trend in developing country like India. Study Objectives: To assess the knowledge, attitude and practices (KAPs) related to the prevention and control of dengue fever (DF) among frontline staff members at a medical teaching institution in Rishikesh, Uttarakhand. Materials and Methods: A community-based cross-sectional study was conducted at a medical teaching institution in Rishikesh, Uttarakhand. Out of 830 frontline workers only 208 workers were recruited in a study by the simple random selection method. A semi-structured interview questionnaire was applied to assess the KAPs of participants. Attitude was assessed by four-point Likert scaling. Statistical analysis was done using SPSS version 23 for Windows. Results: A total of 208 participants were interviewed. Majority were male (70.2%) with the age group of 31 to 45 years (71.2%). Majority (50.5%) of participants were educated up to higher secondary and working as a security guard (78.8%). Most (72.6%) of the respondents said the rainy season was the most common outbreak season for dengue. Most (63.6%) of the participants were aware that dengue is transmitted by mosquitoes. The majority (49%) of participants strongly agreed that dengue is a fatal disease. Conclusion: There is an urgent need to prevent and control the epidemics of dengue by adoption of seven plus one model which contributes in reducing the overall burden in healthcare delivery system.

Molecular docking analysis of mosquito ribosomal protein in selenium nanoparticle bio-synthesis: Implications for pest and pathogen mitigation

BackgroundInsects, rich in diverse proteins, are crucial in nanoparticle biofabrication. This study explores mosquito proteins' potential to reduce selenium ions and produce Selenium nanoparticles (SeNPs). MethodsMosquito larval protein composition was determined via liquid chromatography-mass spectrometry (LC-MS). Molecular docking validated cytoskeletal proteins' efficacy, notably 40S ribosomal protein S7 (binding energy: -6.23) and β-tubulin (binding energy: -5.94), in facilitating selenium ion conversion to SeNPs. SeNPs, mediated by these proteins, were characterized using Ultra Violet-visible spectroscopy, revealing a peak at 295 nm. FT-IR analysis identified biomolecules responsible for capping SeNPs and converting selenious acid to SeNPs. Significant findingsLC-MS detected β-tubulin (1 peptide, 76 amino acids, 8.2 kDa) and 40S ribosomal protein S7 (2 peptides, 192 amino acids, 22.1 kDa). The FT-IR analysis showed peaks at 3420.89 (OH stretch), 2928.35 (aromatic CH stretch), 2344.02 (CC alkynes stretches), etc. X-Ray Diffraction confirmed SeNPs' crystalline structure. Scanning electron microscopy and transmission electron microscopy revealed smooth-surfaced SeNPs in spherical and rod-shaped forms. SDS PAGE analysis post-SeNPs synthesis confirmed 40S ribosomal protein S7 and β-tubulin presence. SeNPs exhibited antibacterial, anti-biofilm, antioxidant, photocatalytic, and insecticidal activities. Median lethal concentrations were 17.674 μg/mL for Culex quinquefasciatus, 31.117 μg/mL for Aedes aegypti, and 81.95 μg/mLfor R. dominica at 48 h. SeNPs suppressed S. aureus biofilm by 33.06 ± 8.26 % and E. coli by 13.8 ± 3.63 %. Vero cells showed no harm at 250 µg/mL SeNPs. At 100 μg/mL, SeNPs exhibited 52.94 % free radical scavenging, compared to 74 % for ascorbic acid. Protein-mediated nanoparticle preparation is favoured for biomedical applications due to ease of synthesis, eco-friendliness, conjugation capability, simple preparation, and utilization of pests.

Role of arylalkylamine N-acetyltransferase 7 in reproduction and limb pigmentation of Aedes aegypti.

Arylalkylamine N-acetyltransferase (aaNAT) is a crucial enzyme that catalyses the transfer of acetyl groups from acetyl coenzyme A to arylalkylamines and arylamines. Evolutionary studies have identified a distinct class of aaNATs specific to mosquitoes, yet their functions remain elusive. This study focuses on Ae-aaNAT7, a mosquito-unique gene in Aedes aegypti (Diptera:Culicidae),to explore its functionality. Temporal and spatial expression analysis of Ae-aaNAT7 mRNA revealed high expression during embryonic development and in first-instar larvae, with notable expression in the limbs of adult mosquitoes based on tissue expression profiling. By further employing CRISPR/Cas9 technology for loss-of-function studies, our investigation revealed a reduction in the area of white spotting in the limbs of Ae-aaNAT7 mutant adult mosquitoes. Further investigation revealed a significant decrease in the fecundity and hatchability of the mutants. Dissection of the ovaries from Ae-aaNAT7 heterozygous mutants showed a noticeable reduction in the oocyte area compared with wild type. Dissection of the exochorion of the eggs from Ae-aaNAT7 homozygous mutants consistently revealed a striking absence of mature embryos. In addition, RNA interference experiments targeting Ae-aaNAT7 in males resulted in a reduction in fecundity, but no effect on hatchability was observed. These collective insights underscore the substantial impact of Ae-aaNAT7 on reproduction and its pivotal contribution to adult limb pigmentation in Ae. aegypti. These revelations offer insights pivotal for the strategic design of future insecticide targets.

The larvicidal efficacy and mechanism of action of 5-Ethenyl-2,2′-bithiophene extracted from Echinops ritro on Aedes aegypti larvae

Herein, we focused on the larvicidal effects and potential mechanisms of 5-ethenyl-2,2′-bithiophene (5 EB), a compound isolated from Echinops ritro L. on Aedes aegypti larvae. Our results show that 5 EB exhibits pronounced larvicidal activity against A. aegypti larvae, with an LC50 = 0.24 mg/L, considerably lesser than that of the traditional insecticide, rotenone. Observations using fluorescence microscopy, electron microscopy, and imaging flow cytometry demonstrated that 5 EB targets the hemocytes of larvae, leading to the disruption of their intracellular membrane systems. This disruption leads to considerable damage to the cellular structure and function, leading to the death of test subjects. Note that additional investigation into the molecular mechanism of 5 EB's action was conducted using transcriptomic analysis. Both GO and KEGG enrichment analyses reported that the differentially expressed genes were predominantly associated with membranes, lysosomes, and catalytic activities. To summarize, this study provides new options for developing new, environmentally friendly, plant-based larvicides for mosquito control.

Recombinant Beauveria bassiana expressing Bacillus thuringiensis toxin Cyt1Aa: a promising approach for enhancing Aedes mosquito control.

Beauveria bassiana is a naturally occurring fungus that can be utilized as a bioinsecticide against mosquitoes. Cyt1Aa is a delta-endotoxin protein produced by Bacillus thuringiensis that exhibits specific and potent insecticidal activity against mosquitoes. In our study, the expression of this toxin Cyt1Aa in B. bassiana enhances the virulence of B. bassiana against Aedes aegypti and Aedes albopictus, thereby increasing their effectiveness in killing mosquitoes. This novel strain can be used alongside chemical insecticides to reduce dependence on harmful chemicals, thereby minimizing negative impacts on the environment and human health. Additionally, the potential resistance of B. bassiana against mosquitoes in the future could be overcome by acquiring novel combinations of exogenous toxin genes. The presence of B. bassiana that expresses Cyt1Aa is of significant importance in mosquito control as it enhances genetic diversity, creates novel virulent strains, and contributes to the development of safer and more sustainable methods of mosquito control.

Dengue Virus Serotype 1 Effects on Mosquito Survival Differ among Geographically Distinct Aedes aegypti Populations.

The mosquito Aedes aegypti is distributed worldwide and is recognized as the primary vector for dengue in numerous countries. To investigate whether the fitness cost of a single DENV-1 isolate varies among populations, we selected four Ae. aegypti populations from distinct localities: Australia (AUS), Brazil (BRA), Pakistan (PAK), and Peru (PER). Utilizing simple methodologies, we concurrently assessed survival rates and fecundity. Overall, DENV-1 infection led to a significant decrease in mosquito survival rates, with the exception of the PER population. Furthermore, infected Ae. aegypti from PAK, the population with the lowest infection rate among those tested, exhibited a noteworthy reduction in egg laying. These findings collectively suggest that local mosquito-virus adaptations may influence dengue transmission in endemic settings.

High Frequencies of kdr Mutation and Chikungunya Infection in Aedes aegypti Population from Minas Gerais, Brazil.

The Chikungunya virus (CHIKV) presents global health challenges, with Brazil experiencing outbreaks since its introduction in 2014. In 2023, following a CHIKV outbreak in Minas Gerais (MG), social media was used to optimize an entomological survey aimed at identifying vectors and viral lineages and assessing insecticide resistance. Following Instagram posts, residents with suspected CHIKV infection were able to schedule mosquito aspirations. In total, 421 mosquitoes (165 Aedes aegypti and 256 Culex quinquefasciatus) were captured from 40 households in Salinas city (MG) and tested for the Dengue, Zika, and Chikungunya viruses through RT-qPCR. Twelve of 57 pools (10 Ae. aegypti and two Cx. quinquefasciatus) tested positive for CHIKV RNA. Viral RNA was also detected in the heads of nine Ae. aegypti, indicating viral dissemination but not in Cx. quinquefasciatus. Genome sequencing yielded the first near-complete genome from the 2023 outbreak, unveiling that the CHIKV strain belonged to the East/Central/South African (ECSA) genotype. Additionally, genetic analyses revealed high frequencies of kdr alleles, including in CHIKV-infected mosquitoes, suggesting resistance to pyrethroid insecticides in this Ae. aegypti population. Social media was important for guiding mosquito-capture efforts in CHIKV transmission hotspots, thus optimizing the opportunity for viral detection. These findings emphasize the urgent need for innovative vector studies and control strategies, as well as interdisciplinary approaches in public health interventions.

Cost of controlling the dengue vector Aedes aegypti in the Peruvian amazon.

Motivation for the study. Dengue prevention and control is based on the control of its vector. This study was conducted because of the need to know the costs associated with Aedes aegypti control in a region that carries out planned vector control activities. Main findings. The costs incurred in dengue vector control in the Loreto region in 2017 and 2018 amounted to PEN 4,066,380.25 and PEN 3,807,858.73, respectively. Implications. Knowing the cost of vector control activities will allow us to better plan these activities and have a basis for cost-effectiveness studies with other methods of prevention and control of dengue. To estimate the costs incurred in the control of Aedes aegypti in the Loreto region, during the years 2017 and 2018. We conducted a partial retrospective economic evaluation of the costs of Aedes aegypti control of the Regional Health Directorate Loreto, during the implementation of the Regional Plan for Surveillance and Control of Aedes aegypti. Documentation such as plans, intervention reports and payment slips were reviewed, and interviews were conducted with professional personnel involved in vector control, on the costs of control interventions. We found that the costs incurred in dengue vector control in the Loreto Region in the two years were: PEN 3,807,858 and PEN 4,066,380 during 2017 and 2018, respectively (USD 1,175,264 and USD 1,1210,232 at the 2017 and 2018 exchange rate). However, the effect of control activities is short-lived. The high cost involved in vector control with the methods currently used and the short duration of its effect make it unsustainable. Studies should be conducted in order to find other more efficient methods for dengue control.

Use of glycerin in strategies against Aedes aegypti mosquito

Use of glycerin in strategies against Aedes aegypti mosquito

Diversity of Wolbachia infections in Sri Lankan mosquitoes with a new record of Wolbachia Supergroup B infecting Aedes aegypti vector populations

Wolbachia bacteria are common endosymbionts of insects and have recently been applied for controlling arboviral vectors, especially Aedes aegypti mosquito populations. However, several medically important mosquito species in Sri Lanka were present with limited information for the Wolbachia infection status. Therefore, the screening of Wolbachia in indigenous mosquitoes is required prior to a successful application of Wolbachia-based vector control strategy. In this study, screening of 78 mosquito species collected from various parts of the country revealed that 13 species were positive for Wolbachia infection, giving ~ 17% infection frequency of Wolbachia among the Sri Lankan mosquitoes. Twelve Wolbachia-positive mosquito species were selected for downstream Wolbachia strain genotyping using Multi Locus Sequencing Type (MLST), wsp gene, and 16S rRNA gene-based approaches. Results showed that these Wolbachia strains clustered together with the present Wolbachia phylogeny of world mosquito populations with some variations. Almost 90% of the mosquito populations were infected with supergroup B while the remaining were infected with supergroup A. A new record of Wolbachia supergroup B infection in Ae. aegypti, the main vectors of dengue, was highlighted. This finding was further confirmed by real-time qPCR, revealing Wolbachia density variations between Ae. aegypti and Ae. albopictus (p = 0.001), and between males and females (p < 0.05). The evidence of natural Wolbachia infections in Ae. aegypti populations in Sri Lanka is an extremely rare incident that has the potential to be used for arboviral vector control.

MATHEMATICAL MODEL OF REPELLENT EFFECT IN DENGUE TRANSMISSION

Dengue is a disease caused by the dengue virus, transmitted through the bite of an infected female Aedes aegypti. Dengue virus is a member of the genus Flavivirus, family Flaviviridae. Indonesia is one of the countries with the most dengue cases in Southeast Asia. Therefore, dengue transmission must be controlled to reduce the increase in dengue cases. One of the controls is by using repellents. Repellent is one of the human protection strategies to avoid mosquito bites used by spraying or smearing. This study models dengue transmission by reviewing the effect and control of repellent. A mathematical model of repellent effect and control in dengue transmission uses a SIR compartment model. The SIR model is modified by involving mosquitoes and the human population. Repellent is used in both susceptible humans, infected humans, and recovered humans. Numerical and analytical simulations are conducted to analyze the behavior of each compartment of the mosquito and human populations in dengue transmission. Analytical results show that the factors affecting the spread of infection are the transmission rate of the dengue virus and the loss of human-repellent protection. The transmission rate of dengue virus in the interval increases the infected human by 2.73%, while the rate of loss of human repellent protection in the interval increases the infected human by 0.03%. Optimal control is used to minimize the number of infected humans who do not use repellent. The results of numerical simulations on the optimal control problem show that an increase in the proportion of healthy humans who have campaign effect and use repellent regularly in the range of 14.67% can reduce infected individuals by 0.647%.

Molecular characterization of Aedes aegypti (L.), its bacterial microbiomes and their control in Saudi Arabia

Aim: This study aims to identify laboratory strains of Aedes aegypti at a molecular level and isolate bacteria from various developmental stages, while also assessing the effectiveness of environmentally friendly Bacillus subtilis compared to a commercial insecticide (Bacilod 5000 IU) containing Bacillus thuringiensis against the 4th larval stage of Ae. aegypti. Methodology: The molecular analysis revealed a new strain of Ae. aegypti and identified 24 bacterial strains from 9 distinct families. These novel strains were documented and deposited in the GenBank for future reference. Notably, in this study B. subtilis at different concentrations (1000, 3000, 5000, 7000 and 9000 ppm) was compared with Bacilod 5000 IU (0.1, 0.3, 0.5, 0.8 and 1 ppm). Results: The mortality rate of 4th instar larvae ranged from 12 to 93% for strains treated with the isolated bacteria B. subtilis and 14 to 92% for strains treated with the commercial insecticide B. thuringiensis IU. In comparison to B. subtilis, the commercial insecticide B. thuringiensis showed an approximate 8939.91 times higher relative resistance index. Interpretation: The results obtained in this study highlights the need for further research into isolated bacteria as potential biological controls for Ae. aegypti. Key words: Aedes aegypti, Bacillus subtilis, Biological control, Insecticides, Microbiomes

Fatally impaired glucose digestion by propylene glycol in Aedes aegypti (Diptera: Culicidae) and co-formulation with terpenoids for enhancing attractive toxic sugar baits.

Propylene glycol (PG) demonstrates greater efficacy than other sugar polyols. However, the attributes it confers for toxicity and possible co-formulation with other ingredients are unknown. To evaluate this, α-glucosidase and glucose oxidase reactions were performed in Aedes aegypti (L.) (Diptera: Culicidae) to categorize if PG behaves similarly to prior studied sugar alcohols. A combination of no-choice and choice assays was used to determine effective ratios of PG and sucrose, competitiveness against a control of 10% sucrose, and whether mosquitoes recovered from PG consumption. The final trials included β-cyclodextrin encapsulated cinnamon leaf oil, clove stem oil, patchouli oil, garlic oil, cedarwood oil, and papaya seed oil formulated with 5% sucrose + 5% PG. PG functioned as a linear competitive inhibitor of α-glucosidase. The efficacy of PG was synergized by co-ingestion with equivalent ratios of sucrose. Unlike the high diuretic response to other sugar alcohols, PG resulted in diminished excretion regardless of being co-formulated with sucrose or terpenoids. PG is not especially competitive against unadulterated sugar meals but is likewise not clearly repellent. Although mosquitoes did not recover from ingestion of the glycol meals, there was no indication that mortality would continue to accumulate once the treatments were removed. Of the terpenoids tested, cinnamon and patchouli caused ~50% or less mortality; garlic, cedarwood, and clove caused 80-90% mortality; and papaya seed caused 100% mortality, exceeding all other test groups and the formulation blank. PG is a useful supporting ingredient in attractive toxic sugar bait formulations with flexibility in formulation.