scholarly journals Establishment of Wolbachia strain wAlbB in Malaysian populations of Aedes aegypti for dengue control

2019 ◽  
Author(s):  
W. A. Nazni ◽  
A. A. Hoffmann ◽  
A. Noor Afizah ◽  
Y. L. Cheong ◽  
M. V. Mancini ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Virus Transmission ◽  
Larval Rearing ◽  
Kuala Lumpur ◽  
Novel Approach ◽  
Dengue Transmission ◽  
Vector Mosquito ◽  
Primary Vector ◽  
Dengue Control ◽  
Very High

AbstractDengue has enormous health impacts globally. A novel approach to decrease dengue incidence involves the introduction of Wolbachia endosymbionts that block dengue virus transmission into populations of the primary vector mosquito, Aedes aegypti. The wMel Wolbachia strain has previously been trialed in open releases of Ae. aegypti; however the wAlbB strain has been shown to maintain higher density than wMel at high larval rearing temperatures. Releases of Ae. aegypti mosquitoes carrying wAlbB were carried out in 6 diverse sites in greater Kuala Lumpur, Malaysia, with high endemic dengue transmission. The strain was successfully established and maintained at very high population frequency at some sites, or persisted with additional releases following fluctuations at other sites. Based on passive case monitoring, reduced human dengue incidence was observed in the release sites when compared to control sites. The wAlbB strain of Wolbachia provides a promising option as a tool for dengue control, particularly in very hot climates.

scholarly journals High temperature cycles result in maternal transmission and dengue infection differences between Wolbachia strains in Aedes aegypti

2020 ◽  
Author(s):  
Maria Vittoria Mancini ◽  
Thomas H. Ant ◽  
Christie S. Herd ◽  
Daniel D. Gingell ◽  
Shivan M. Murdochy ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Aedes Aegypti ◽  
Virus Transmission ◽  
Temperature Cycle ◽  
Larval Rearing ◽  
Mosquito Vector ◽  
Maternal Transmission ◽  
Rearing Temperature ◽  
Dengue Control ◽  
The Impact

AbstractEnvironmental factors play a crucial role in the population dynamics of arthropod endosymbionts, and therefore in the deployment of Wolbachia symbionts for the control of dengue arboviruses. The potential of Wolbachia to invade, persist and block virus transmission depends in part on its intracellular density. Several recent studies have highlighted the importance of larval rearing temperature in modulating Wolbachia densities in adults, suggesting that elevated temperatures can severely impact some strains, while having little effect on others. The effect of a replicated tropical heat cycle on Wolbachia density and levels of virus blocking was assessed using Aedes aegypti lines carrying strains wMel and wAlbB, two Wolbachia strains currently used for dengue control. Impacts on intracellular density, maternal transmission fidelity and dengue inhibition capacity were observed for wMel. In contrast wAlbB-carrying Ae. aegypti maintained a relatively constant intracellular density at high temperatures and conserved its capacity to inhibit dengue. Following larval heat treatment, wMel showed a degree of density recovery in aging adults, although this was compromised by elevated air temperatures. When choosing the Wolbachia strain to be used in a dengue control programme it is important to consider the effects of environmental temperatures on invasiveness and virus inhibition.Author summaryIn the past decades, dengue incidence has dramatically increased all over the world. An emerging dengue control strategy utilizes Ae. aegypti mosquitoes artificially transinfected with the bacterial symbiont Wolbachia, with the ultimate aim of replacing wild mosquito populations. Wolbachia is transmitted from mother to offspring and is able to interfere with virus transmission within the mosquito vector. However, the rearing temperature of mosquito larvae is known to impact on some Wolbachia strains. In this study, we compared the effects of a temperature cycle mimicking natural breeding sites in tropical climates on two Wolbachia strains, currently used for open field trials. We observed that the strain wMel was susceptible to high larval rearing temperatures, while the strain wAlbB resulted to be more stable. These results underlines the importance of understanding the impact of environmental factors on released mosquitoes, in order to ensure the most efficient strategy for dengue control.

scholarly journals Wolbachia strain w AlbB maintains high density and dengue inhibition following introduction into a field population of Aedes aegypti

2020 ◽  
Vol 376 (1818) ◽  
pp. 20190809 ◽  
Author(s):  
Noor Afizah Ahmad ◽  
Maria-Vittoria Mancini ◽  
Thomas H. Ant ◽  
Julien Martinez ◽  
Ghazali M. R. Kamarul ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Control Strategies ◽  
Scale Up ◽  
Virus Transmission ◽  
Kuala Lumpur ◽  
Virus Dissemination ◽  
Laboratory Colony ◽  
Dengue Control ◽  
Additional Support

Aedes aegypti mosquitoes carrying the w AlbB Wolbachia strain show a reduced capacity to transmit dengue virus. w AlbB has been introduced into wild Ae. aegypti populations in several field sites in Kuala Lumpur, Malaysia, where it has persisted at high frequency for more than 2 years and significantly reduced dengue incidence. Although these encouraging results indicate that w AlbB releases can be an effective dengue control strategy, the long-term success depends on w AlbB maintaining high population frequencies and virus transmission inhibition, and both could be compromised by Wolbachia– host coevolution in the field. Here, w AlbB-carrying Ae. aegypti collected from the field 20 months after the cessation of releases showed no reduction in Wolbachia density or tissue distribution changes compared to a w AlbB laboratory colony. The w AlbB strain continued to induce complete unidirectional cytoplasmic incompatibility, showed perfect maternal transmission under laboratory conditions, and retained its capacity to inhibit dengue. Additionally, a field-collected w AlbB line was challenged with Malaysian dengue patient blood, and showed significant blocking of virus dissemination to the salivary glands. These results indicate that w AlbB continues to inhibit currently circulating strains of dengue in field populations of Ae. aegypti , and provides additional support for the continued scale-up of Wolbachia wAlbB releases for dengue control. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases’.

scholarly journals Microbes increase thermal sensitivity in the mosquito Aedes aegypti, with the potential to change disease distributions

2021 ◽  
Vol 15 (7) ◽  
pp. e0009548
Author(s):  
Fhallon Ware-Gilmore ◽  
Carla M. Sgrò ◽  
Zhiyong Xi ◽  
Heverton L. C. Dutra ◽  
Matthew J. Jones ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Thermal Tolerance ◽  
Biological Control Agent ◽  
Thermal Sensitivity ◽  
Virus Transmission ◽  
Denv Infection ◽  
Control Agent ◽  
Thermal Limits ◽  
Primary Vector ◽  
Global Mean

The mosquito Aedes aegypti is the primary vector of many disease-causing viruses, including dengue (DENV), Zika, chikungunya, and yellow fever. As consequences of climate change, we expect an increase in both global mean temperatures and extreme climatic events. When temperatures fluctuate, mosquito vectors will be increasingly exposed to temperatures beyond their upper thermal limits. Here, we examine how DENV infection alters Ae. aegypti thermotolerance by using a high-throughput physiological ‘knockdown’ assay modeled on studies in Drosophila. Such laboratory measures of thermal tolerance have previously been shown to accurately predict an insect’s distribution in the field. We show that DENV infection increases thermal sensitivity, an effect that may ultimately limit the geographic range of the virus. We also show that the endosymbiotic bacterium Wolbachia pipientis, which is currently being released globally as a biological control agent, has a similar impact on thermal sensitivity in Ae. aegypti. Surprisingly, in the coinfected state, Wolbachia did not provide protection against DENV-associated effects on thermal tolerance, nor were the effects of the two infections additive. The latter suggests that the microbes may act by similar means, potentially through activation of shared immune pathways or energetic tradeoffs. Models predicting future ranges of both virus transmission and Wolbachia’s efficacy following field release may wish to consider the effects these microbes have on host survival.

scholarly journals Short Report: Adult Aedes abundance and risk of dengue transmission

2021 ◽  
Vol 15 (6) ◽  
pp. e0009475
Author(s):  
Janet Ong ◽  
Joel Aik ◽  
Lee Ching Ng
Keyword(s):  
Aedes Aegypti ◽  
Adult Female ◽  
Cluster Formation ◽  
Fold Increase ◽  
Short Report ◽  
Dengue Case ◽  
Vector Surveillance ◽  
Dengue Transmission ◽  
The Impact ◽  
Very High

Dengue is transmitted mainly by the adult female Aedes aegypti mosquito. However, little is known about the impact of adult Aedes abundance on the risk of dengue transmission. Here we analysed nationally representative dengue case and vector surveillance data collected from Singapore, to determine the effect of adult Aedes abundance on the risk of dengue transmission. A case was an area with active dengue transmission as indicated by the presence of dengue cluster. A control was an area where no dengue cluster was reported. Using multivariate logistic regression, we analysed 88 cases and 602 controls and estimated the odds of dengue cluster formation at various adult Aedes abundance levels, estimated by the mean number of adult female Aedes per Gravitrap per week and categorised into Low, Moderate, High and Very High abundance level. We found that the risk of dengue cluster formation was positively associated with adult Ae. aegypti abundance. We observed a three to four-fold increase in the odds of dengue clusters forming in areas with High (AOR: 3.40, 95% CI: 2.09, 5.52) and Very High (AOR: 3.99, 95% CI: 2.46, 6.46) adult Aedes aegypti abundance level compared to those with low Ae. aegypti abundance level. Our study strengthens the evidence for the use of adult Aedes indices for dengue risk assessment and early warning for dengue outbreaks. Entomological indicators of adult Ae. aegypti could be used to anticipate and prioritize areas for dengue control.

scholarly journals Resistance of Aedes aegypti (Diptera: Culicidae) Populations to Deltamethrin, Permethrin, and Temephos in Cambodia

2018 ◽  
Vol 30 (2) ◽  
pp. 158-166 ◽  
Author(s):  
Sébastien Boyer ◽  
Sergio Lopes ◽  
Didot Prasetyo ◽  
John Hustedt ◽  
Ay Sao Sarady ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Vector Control ◽  
Sensitive Strain ◽  
World Health ◽  
Health Concern ◽  
Rural And Urban ◽  
Urban Classification ◽  
Dengue Transmission ◽  
Primary Vector ◽  
Health Organization

Dengue fever is a major public health concern, including 185,000 annual cases in Cambodia. Aedes aegypti is the primary vector for dengue transmission and is targeted with insecticide treatments. This study characterized the insecticide resistance status of Ae aegypti from rural and urban locations. The susceptibility to temephos, permethrin, and deltamethrin of Ae aegypti was evaluated in accordance with World Health Organization instructions. All the field populations showed lower mortality rate to temephos compared with the sensitive strain with resistance ratio 50 (RR50) varying from 3.3 to 33.78 and RR90 from 4.2 to 47 compared with the sensitive strain, demonstrating a generalized resistance of larvae to the temephos in Cambodia. Ae aegypti adult populations were highly resistant to permethrin regardless of province or rural/urban classification with an average mortality of 0.02%. Seven of the 8 field populations showed resistance to deltamethrin. These results are alarming for dengue vector control, as widespread resistance may compromise the entomological impact of larval control operations. Innovative vector control tools are needed to replace ineffective pesticides in Cambodia.

First Record of Aedes aegypti (L.) Vector of Dengue Virus from Kathmandu, Nepal

2009 ◽  
Vol 24 ◽  
pp. 156 ◽  
Author(s):  
Ishan Gautam ◽  
Megh Nath Dhimal ◽  
Shambhu Raj Shrestha ◽  
Anand Shova Tamrakar
Keyword(s):  
Natural History ◽  
Aedes Aegypti ◽  
First Record ◽  
Transmission Risk ◽  
Haemorrhagic Fever ◽  
Survey Techniques ◽  
Breeding Habitats ◽  
Larval Survey ◽  
Imported Cases ◽  
Primary Vector

Aedes aegypti is the primary vector for the transmission of Dengue Fever (DF)/Dengue Haemorrhagic Fever (DHF). Entomological investigations on breeding habitats and larval prevalence of mosquitoes Aedes aegypti (L.) and Ae. albopictus (Skuse) were conducted from April to June 2009 in Kathmandu district, Nepal. Different water-filled containers were examined for the presence or absence of Aedes larvae. Larval survey techniques were used to obtain the House Index (HI), Container Index (CI) and Breteau Index (BI). The over all HI, CI and BI for Aedes aegypti were 6.25, 4.83, 9.37 and for Aedes albopictus were 6.25, 3.22 and 6.25 respectively. It was also observed that discarded tires lying outdoors were the preferred breeding habitats. No breeding was observed in other containers in April and May during this three months survey. Herewith, we report the first collection and identification of Aedes aegypti in Kathmandu during June, 2009. Indeed, this finding constitutes the first record from the capital of Nepal within the urban agglomeration of Basundhara and Gongabu-Balaju area.Therefore, DF/DHF transmission risk may occur locally if imported cases are introduced.  Key Words: Aedes aegypti; Ae. albopictus;  Kathmandu; First record; Dengue Fever.Journal of Natural History MuseumVol 24, 2009.Page:

scholarly journals The Lethal(2)-Essential-for-Life [L(2)EFL] Gene Family Modulates Dengue Virus Infection in Aedes aegypti

2020 ◽  
Vol 21 (20) ◽  
pp. 7520
Author(s):  
Lucky R. Runtuwene ◽  
Shuichi Kawashima ◽  
Victor D. Pijoh ◽  
Josef S. B. Tuda ◽  
Kyoko Hayashida ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Dengue Virus ◽  
Cell Line ◽  
Dengue Infection ◽  
Fruit Fly ◽  
Initiation Factor ◽  
Poly I:C ◽  
Gene Products ◽  
Vector Mosquito

Efforts to determine the mosquito genes that affect dengue virus replication have identified a number of candidates that positively or negatively modify amplification in the invertebrate host. We used deep sequencing to compare the differential transcript abundances in Aedes aegypti 14 days post dengue infection to those of uninfected A. aegypti. The gene lethal(2)-essential-for-life [l(2)efl], which encodes a member of the heat shock 20 protein (HSP20) family, was upregulated following dengue virus type 2 (DENV-2) infection in vivo. The transcripts of this gene did not exhibit differential accumulation in mosquitoes exposed to insecticides or pollutants. The induction and overexpression of l(2)efl gene products using poly(I:C) resulted in decreased DENV-2 replication in the cell line. In contrast, the RNAi-mediated suppression of l(2)efl gene products resulted in enhanced DENV-2 replication, but this enhancement occurred only if multiple l(2)efl genes were suppressed. l(2)efl homologs induce the phosphorylation of eukaryotic initiation factor 2α (eIF2α) in the fruit fly Drosophila melanogaster, and we confirmed this finding in the cell line. However, the mechanism by which l(2)efl phosphorylates eIF2α remains unclear. We conclude that l(2)efl encodes a potential anti-dengue protein in the vector mosquito.

scholarly journals Behavioural response of mosquito vectors Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus to synthetic pyrethroid and organophosphorus-based slow-release insecticidal paint

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Sunil Dhiman ◽  
Kavita Yadav ◽  
B. N. Acharya ◽  
Raj Kumar Ahirwar ◽  
D. Sukumaran
Keyword(s):  
Aedes Aegypti ◽  
Culex Quinquefasciatus ◽  
Anopheles Stephensi ◽  
Slow Release ◽  
Disease Risk ◽  
Mosquito Species ◽  
Escape Time ◽  
Behavioural Avoidance ◽  
Vector Mosquito ◽  
Contact Exposure

Abstract Background The direct toxicological impact of insecticides on vector mosquitoes has been well emphasized; however, behavioural responses such as excito-repellency and physical avoidance as a result of insecticide exposure have not been much studied. We have demonstrated the excito-repellency and behavioural avoidance in certain vector mosquito species on exposure to a slow-release insecticidal paint (SRIP) formulation in addition to direct toxicity. Methods A SRIP formulation developed by the Defence Research and Development Establishment, Gwalior, contains chlorpyriphos, deltamethrin and pyriproxyfen as active insecticides. Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti mosquitoes were used to study the excito-repellency response of the formulation. The experiments were performed in a specially designed dual-choice exposure and escape chamber made of transparent polymethyl methacrylate. For the experiments, the SRIP formulation was applied undiluted at a rate of 8 m2 per kg on 15 cm2 metallic surfaces. Mosquitoes were introduced into the exposure chamber, and observations of the movement of mosquitoes into the escape chamber through the exit portal were taken at 1-min intervals for up to 30 min. Results The evaluated formulation displayed strong excito-repellency against all three tested vector mosquito species. Results showed that the ET50 (escape time 50%) for Ae. aegypti, An. stephensi and Cx. quinquefasciatus was 20.9 min, 14.5 min and 17.9 min for contact exposure (CE) respectively. Altogether in CE, the escape rates were stronger in An. stephensi mosquitoes at different time intervals compared to Ae. aegypti and Cx. quinquefasciatus mosquitoes. The probit analysis revealed that the determined ET did not deviate from linearity for both non-contact exposure (NCE) and placebo exposure (PE) (χ2 ≤ 7.9; p = 1.0) for Ae. aegypti mosquitoes and for NCE (χ2 = 8.3; p = 1.0) and PE (χ2 = 1.7; p = 1.0) treatments in Cx. quinquefasciatus. Mortality (24 h) was found to be statistically higher (F = 6.4; p = 0.02) in An. stephensi for CE but did not vary for NCE (p ≥ 0.3) and PE (p = 0.6) treatments among the tested mosquito species. Survival probability response suggested that all the three tested species displayed similar survival responses for similar exposures (χ2 ≤ 2.3; p ≥ 0.1). Conclusion The study demonstrates the toxicity and strong behavioural avoidance in known vector mosquito species on exposure to an insecticide-based paint formulation. The combination of insecticides in the present formulation will broaden the overall impact spectrum for protecting users from mosquito bites. The efficacy data generated in the study provide crucial information on the effectiveness of the tested formulation and could be useful in reducing the transmission intensity and disease risk in endemic countries.

Current Status of Pyrethroids Resistance in Aedes aegypti (Culicidae: Diptera) in Lahore District, Pakistan: A Novel Mechanistic Insight

2021 ◽  
Author(s):  
Saira Nawaz ◽  
Hafiz Muhammad Tahir ◽  
Muhammad Asif Mahmood ◽  
Muhammad Summer ◽  
Shaukat Ali ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Enzyme Level ◽  
Laboratory Strain ◽  
Current Status ◽  
Glutathione S Transferase ◽  
Development Of Resistance ◽  
Biochemical Assays ◽  
Dengue Transmission ◽  
Lambda Cyhalothrin ◽  
Glutathione S Transferases

Abstract Aedes aegypti (Linnaeus, 1762) is a major vector responsible for dengue transmission. Insecticides are being used as the most effective tool to control vector populations in Lahore, Pakistan. Control of Ae. aegypti is threatened by the development of resistance against insecticides. The current status of insecticide resistance was evaluated against pyrethroids (deltamethrin, cypermethrin, and lambda-cyhalothrin) in different populations of Lahore (Model Town, Mishri Shah, Sadar Cantt, Walton, and Valencia). The susceptibility of the larval and adult populations was tested following the standard WHO guidelines. Moderate to high levels of resistance were found against pyrethroids in the larval (RR50: 3.6–27.2 and RR90: 5–90) and adult populations (percentage mortality < 98%). Biochemical assays revealed a statistically significant increase in the enzyme level in all field populations compared to the laboratory strain. The value of esterase was one-fold higher, monooxygenase was 3.9- to 4.7-fold higher, and glutathione S-transferases was 1.9- to 2.6-fold higher in field populations compared to the laboratory strain. These results depict the presence of resistance against deltamethrin, cypermethrin, and lambda-cyhalothrin in field populations of Lahore mediated by metabolic enzymes i.e. esterases, monooxygenases, and glutathione S-transferase.

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