Resistant Aedes Research Articles

A genomic amplification affecting a carboxylesterase gene cluster confers organophosphate resistance in the mosquito Aedes aegypti: From genomic characterization to high-throughput field detection.

By altering gene expression and creating paralogs, genomic amplifications represent a key component of short‐term adaptive processes. In insects, the use of insecticides can select gene amplifications causing an increased expression of detoxification enzymes, supporting the usefulness of these DNA markers for monitoring the dynamics of resistance alleles in the field. In this context, the present study aims to characterize a genomic amplification event associated with resistance to organophosphate insecticides in the mosquito Aedes aegypti and to develop a molecular assay to monitor the associated resistance alleles in the field. An experimental evolution experiment using a composite population from Laos supported the association between the over‐transcription of multiple contiguous carboxylesterase genes on chromosome 2 and resistance to multiple organophosphate insecticides. Combining whole genome sequencing and qPCR on specific genes confirmed the presence of a ~100‐Kb amplification spanning at least five carboxylesterase genes at this locus with the co‐existence of multiple structural duplication haplotypes. Field data confirmed their circulation in South‐East Asia and revealed high copy number polymorphism among and within populations suggesting a trade‐off between this resistance mechanism and associated fitness costs. A dual‐color multiplex TaqMan assay allowing the rapid detection and copy number quantification of this amplification event in Ae. aegypti was developed and validated on field populations. The routine use of this novel assay will improve the tracking of resistance alleles in this major arbovirus vector.

Permethrin Resistance in Aedes aegypti Affects Aspects of Vectorial Capacity

Simple SummaryPyrethroids have been applied as a major type of insecticide targeted at mosquitoes, many of which are key vectors in the transmission of several flaviviruses. Resistance to pyrethroids has emerged and become a worldwide threat to mosquito control. Pyrethroid resistance is usually accompanied by knockdown resistance (kdr) where the voltage gated sodium channel gene is mutated. We selected a permethrin resistant (p-s) Aedes aegypti population from Florida and, along with its parental population, examined two mutation sites, V1016I and F1534C. The data showed the p-s population had the most homozygous mutations which correlated to the permethrin resistance level. To assess the risk of disease transmission, two parameters affecting vectorial capacity were checked. The p-s population showed the longer survival time and higher dissemination rate for dengue compared to its parental population. The results showed that the potential threat of vector-borne diseases was increased in areas with resistant mosquitoes.Aedes aegypti, as one of the vectors transmitting several arboviruses, is the main target in mosquito control programs. Permethrin is used to control mosquitoes and Aedes aegypti get exposed due to its overuse and are now resistant. The increasing percentage of permethrin resistant Aedes aegypti has become an important issue around the world and the potential influence on vectorial capacity needs to be studied. Here we selected a permethrin resistant (p-s) Aedes aegypti population from a wild Florida population and confirmed the resistance ratio to its parental population. We used allele-specific PCR genotyping of the V1016I and F1534C sites in the sodium channel gene to map mutations responsible for the resistance. Two important factors, survival rate and vector competence, that impact vectorial capacity were checked. Results indicated the p-s population had 20 times more resistance to permethrin based on LD50 compared to the parental population. In the genotyping study, the p-s population had more homozygous mutations in both mutant sites of the sodium channel gene. The p-s adults survived longer and had a higher dissemination rate for dengue virus than the parental population. These results suggest that highly permethrin resistant Aedes aegypti populations might affect the vectorial capacity, moreover, resistance increased the survival time and vector competence, which should be of concern in areas where permethrin is applied.

Evidence of Metabolic Resistance in Pyrethroid Resistant Aedes aegypti Population from Lagos, Nigeria

Background: Pyrethroid resistance in Aedes aegypti is of major concern to the control of several arboviral infections. The major mechanisms of Pyrethroid resistance in mosquitoes are target-site insensitivity and elevation in the activity of detoxification enzymes. In this study, we assessed the susceptibility status of Aedes aegypti population from Lagos to Pyrethroid and the impact of metabolic enzymes on resistance development. Methods: Larvae of Aedes aegypti were collected from differ ent habitats in Lagos Mainland Local Government Area, Lagos state. Adult mosquitoes of 2-5 days were exposed to diagnostic dose of permethrin and Deltamethrin using the CDC method. Synergist assay was done with pre-exposure of samples to PBO before exposure to insecticide. Esterase and GST activities were measured using standard protocol. Regression Probit was used to compute the KDT50 and KDT95. Analysis of variance was used to compare the difference in mean of enzymes activities. Results: Aedes aegypti population from the study location is resistant to permethrin (33% ) and Deltamethrin (80%) within the diagnostic time. PBO pre-exposure increases percentage knockdown from 33% to 82% and 80% to 87% for permethrin and Deltamethrin respectively. The activity of GST was higher (P<0.05) in permethrin exposed mosquitoes in comparison with unexposed. Conclusion: A robust insecticide resistance management (IRM) plan in Lagos should take into consideration strategies for addressing the effects of metabolic enzymes in resistance development .

Ecomore 2 project in Cambodia: Integrated vector management for dengue vectors in schools in an entomological/epidemiological approach

Background: In Cambodia, recent results showed very high resistance of Aedes aegypti to temephos, the only larvicide used in Cambodia, and two adulticides (permethrin used for net treatment, and deltamethrin for insecticide fumigation). The Ecomore2 project in Cambodia aims to estimate the effectiveness of an integrated vector management (IVM) targeting schools combined with an educational program to mitigate peaks of dengue and dengue-like syndromes (DLS) for reducing subsequent overcrowding of health centers. Methods and materials: A cluster randomized controlled trial was implemented in 24 clusters (12 under integrated vector control and 12 without), each including one school, with an active surveillance of DLS in neighboring villages. Our research program was also implemented to determine if an IVM could decrease the number of Ae. aegypti mosquitoes in schools by using Bacillus thruringiensis var. israelensis as a larvicide, pyriproxyfen for the dissemination of insect growth regulator larvicide and spores of Beauveria bassiana for slowly killing adults; all these methods were combined with education and sensitization of children. Results: Monitoring of mosquito populations during the first year showed the presence of at least 58 mosquito species, including dengue virus vectors such as Ae. aegypti and Ae. albopictus, but also vector species of Plasmodium spp., and Japanese encephalitis, Rift Valley Fever, West Nile Fever, Zika, Chikungunya and Ross River viruses. Ae. aegypti and Ae. albopictus were present in all 24 schools. There was no difference in the relative abundance of Ae. aegypti and Ae. albopictus between the clusters before the intervention. In parallel, epidemiological data neither showed any baseline difference of DLS. Entomological data following IVM showed a decrease of 50% of Ae. aegypti relative abundance in treated clusters compared to untreated clusters. The latter showed an average relative abundance of Ae. aegypti similar to the first year. The difference for Ae. albopictus relative abundance was not significant between the 2 areas. Epidemiological final data analysis are in progress, but will be presented for the ICID conference. Conclusion: In conclusion, the IVM decreased the Dengue vectors in schools in Cambodia. The epidemiological results of dengue incidence in the 2 clusters will be discussed during the conference.

Metabolic resistance mechanism in Aedes aegypti from Lagos State, Nigeria

BackgroundAedes aegypti transmits several arboviral diseases of global public health threat such as dengue, zika, and yellow fever. Recently, a series of yellow fever outbreaks have been reported in different parts of the country. Globally, the control of mosquito-borne diseases has relied heavily on insecticides based vector control efforts. Therefore, we assessed the susceptibility status to three different classes of WHO approved insecticides and evaluated the importance of detoxifying enzymes on insecticides resistance in Aedes aegypti collected from Lagos State, Nigeria. Aedes aegypti immature stages were collected from suitable habitats in peri-domestic areas of Alimosho, Kosofe, Badagry, and Ibeju-Lekki Local Government Areas (LGAs) of Lagos State, 2–5 days old glucose-fed adult female mosquitoes were exposed to discriminating doses of DDT, permethrin, bendiocarb, and PBO synergist using WHO standard procedure and kits. Identification was through morphological means only.ResultsResistance to DDT and permethrin was recorded in all the LGAs, suspected resistance to bendiocarb was recorded in Aedes aegypti from Alimosho while full susceptibility was recorded in other LGAs. PBO synergist significantly increases the 24 h mortality of DDT and permethrin-resistant Aedes aegypti in all the LGAs. The activities of both GSTs and cytochrome P450s increase with decreasing mortality for Aedes aegypti, regression value (R2) ranges from 0.8889 to 0.6224 for GSTs and 0.4379 to 0.616 for cytochrome P450s.ConclusionsAedes aegypti population from Lagos State, Nigeria, have developed resistance to DDT and permethrin, the activities of P450s and GST were implicated in DDT and permethrin resistance in this study. Therefore, a need for regular insecticides monitoring and PBO should be incorporated into Aedes aegypti insecticides control strategies to forestall development of resistance to DDT and pyrethriods.

The Ras/ERK signaling pathway couples antimicrobial peptides to mediateresistance todengue virusin Aedes mosquitoes.

Aedes mosquitoes can transmit dengue and several other severe vector-borne viral diseases, thereby influencing millions of people worldwide. Insects primarily control and clear the viral infections via their innate immune systems. Mitogen-Activated Protein Kinases (MAPKs) and antimicrobial peptides (AMPs) are both evolutionarily conserved components of the innate immune systems. In this study, we investigated the role of MAPKs in Aedes mosquitoes following DENV infection by using genetic and pharmacological approaches. We demonstrated that knockdown of ERK, but not of JNK or p38, significantly enhances the viral replication in Aedes mosquito cells. The Ras/ERK signaling is activated in both the cells and midguts of Aedes mosquitoes following DENV infection, and thus plays a role in restricting the viral infection, as both genetic and pharmacological activation of the Ras/ERK pathway significantly decreases the viral titers. In contrast, inhibition of the Ras/ERK pathway enhances DENV infection. In addition, we identified a signaling crosstalk between the Ras/ERK pathway and DENV-induced AMPs in which defensin C participates in restricting DENV infection in Aedes mosquitoes. Our results reveal that the Ras/ERK signaling pathway couples AMPs to mediate the resistance of Aedes mosquitoes to DENV infection, which provides a new insight into understanding the crosstalk between MAPKs and AMPs in the innate immunity of mosquito vectors during the viral infection.

Corrigendum.

Insect Molecular BiologyVolume 29, Issue 5 p. 498-498 CorrigendumFree Access Corrigendum This article corrects the following: Exome-wide association of deltamethrin resistance in Aedes aegypti from Mexico K. Saavedra-Rodriguez, C. L. Campbell, A. Lenhart, P. Penilla, S. Lozano-Fuentes, W. C. Black, Volume 28Issue 5Insect Molecular Biology pages: 591-604 First Published online: March 13, 2019 First published: 23 August 2020 https://doi.org/10.1111/imb.12660AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat In the article “Exome-wide association of deltamethrin resistance in Aedes aegypti from Mexico”, by K. Saavedra-Rodriguez et al. [1], the affiliation of coauthor P. Penilla was incorrectly published as “Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, USA”. The correct affiliation should have been “Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, Chiapas, México”. The authors apologize for the error. Reference 1Saavedra-Rodriguez, K., Campbell, C.L., Lenhart, A., Penilla, P., Lozano-Fuentes, S. and Black, W.C.,.I.V. (2019) Exome-wide association of deltamethrin resistance in Aedes aegypti from Mexico. Insect Mol Biol, 28, 591– 604. https://doi.org/10.1111/imb.12575. Volume29, Issue5October 2020Pages 498-498 ReferencesRelatedInformation

Resistance Test of Aedes aegypti Mosquito Larvae Against Organophosphate Insecticides at Medan Selayang

Aedes aegypti is the main vector in several diseases such as Dengue Hemorrhagic Fever (DHF).Various types of efforts to control Aedes aegypti were carried out to terminate the transmission chain by spraying (organizing) the organophosphate insecticide. The use of irrational insecticides causes an increase in esterase enzymes, giving rise to the resistance of Aedes aegypti to insecticides. The purpose of this study is to determine the resistance status of Aedes aegypti larvae to organophosphate insecticides in Medan Selayang. The type of research used in this study is descriptive research with cross-sectional methods, using 276 larvae of Aedes aegypti. The results of this study are mosquito larvae that are susceptible (sensitive) to organophosphate insecticides by 66.3%, while mosquito larvae that are tolerant (moderate resistance) of organophosphate insecticides are 33.7% and resistant (high resistance) mosquito larvae were not found. There is 33.7% of Aedes aegypti larvae are tolerant (moderate resistance) to organophosphate insecticides and resistant (high resistance) mosquito larvae were not found.

Resistance Test of Aedes aegypti Mosquito Larvae Against Organophosphate Insecticides at Medan Selayang

Aedes aegypti is the main vector in several diseases such as Dengue Hemorrhagic Fever (DHF).Various types of efforts to control Aedes aegypti were carried out to terminate the transmission chain by spraying (organizing) the organophosphate insecticide. The use of irrational insecticides causes an increase in esterase enzymes, giving rise to the resistance of Aedes aegypti to insecticides. The purpose of this study is to determine the resistance status of Aedes aegypti larvae to organophosphate insecticides in Medan Selayang. The type of research used in this study is descriptive research with cross-sectional methods, using 276 larvae of Aedes aegypti. The results of this study are mosquito larvae that are susceptible (sensitive) to organophosphate insecticides by 66.3%, while mosquito larvae that are tolerant (moderate resistance) of organophosphate insecticides are 33.7% and resistant (high resistance) mosquito larvae were not found. There is 33.7% of Aedes aegypti larvae are tolerant (moderate resistance) to organophosphate insecticides and resistant (high resistance) mosquito larvae were not found.

The V1016G mutation of the voltage-gated sodium channel (VGSC) gene contributes to the insecticide resistance of Aedes aegypti from Makassar, Indonesia.

Aedes aegypti represents one of the main vectors of at least five relevant arthropod-borne viral infections in humans (i.e., Rift Valley fever, Dengue fever, Zika, chikungunya, and yellow fever) worldwide. Ae. aegypti control strategies are mostly based on using chemical insecticides (i.e., organophosphates, pyrethroids, carbamates, and organochlorines) and reducing larval sources. Furthermore, monitoring the growth activity and mapping the geographical distribution of insecticide resistance are mandatory, as recommended by the WHO. Accordingly, we conducted a study on the possible mechanism by which Ae. aegypti develops resistance to several frequently used chemical insecticides (i.e., λ-cyhalothrin, bendiocarb, cyfluthrin, deltamethrin, malathion, and permethrin) in the city of Makassar, Sulawesi, Indonesia. The results showed the progression of resistance toward the examined insecticides in Ae. aegypti populations in Makassar. The mortality rate of Ae. aegypti was less than 90%, with the highest resistance recorded against 0.75% permethrin. The molecular evaluation of the voltage-gated sodium channel gene (VGSC) showed a significant correlation of the V1016G gene mutation in the tested 0.75% permethrin-resistant Ae. aegypti phenotypes. Nevertheless, the F1534C point mutation in the VGSC gene of Ae. aegypti did not show a significant correlation with the phenotype exhibiting insecticide resistance to 0.75% permethrin. These results indicate that Ae. aegypti mosquitoes in Makassar City have developed resistance against the frequently used insecticide permethrin, which might spread to less-populated regions of Sulawesi. Therefore, we call for further entomological monitoring of insecticide resistance not only on Sulawesi but also on other closely located islands of the Indonesian archipelago to delay the spread of Ae. aegypti insecticide resistance.

Multiple dengue virus serotypes resistant transgenic Aedes aegypti fitness evaluated under laboratory conditions

ABSTRACT Dengue viruses (DENV) are the wildest transmitted arbovirus members of the family Flaviviridae, genus Flavivirus. Dengue viruses are composed of four serotypes, DENV1, 2, 3, and 4, and these viruses can cause dengue fever and dengue haemorrhagic fever or dengue shock syndrome, when infecting humans. RNA interference (RNAi) is a self-defence mechanism, which can be used to prevent invasions of RNA viruses to the host. Genetically engineering a host with an RNAi molecule that targets a single virus serotype may develop escape mutants, and can cause unusual dominance over other serotypes. Therefore, the simultaneous targeting of multiple serotypes is necessary to block DENV transmission. Here, we report the development of transgenic Aedes aegypti based on a bioinformatically designed multiple miRshRNA (microRNA-based shRNA) DNA sequence under the control of a blood-meal induced promoter, Carboxypeptidase A, to induce RNAi for DENV in Aedes aegypti, and demonstrate the expression of a synthetic multiple shRNA polycistronic cluster having RNA interference sequences to target DENV genomes. The transgenic mosquitoes have lower rates of infection, dissemination, and transmission for DENV2 and DENV4 compared to wild mosquitoes, with a significant reduction of dengue copy number and antigen levels in the midgut. These levels of DENV were low enough to make transgenic mosquitoes stop the DENV transmission from infected host to a susceptible host and refractory to DENV2 and DENV4 infection. Such multiple resistance in Ae. aegypti has not been documented previously. Laboratory fitness measurement of transgenic Ae. aegypti showed results comparable to other reported transgenic mosquitoes.

Conventional Detection of Resistance of Aedes aegypti Larvae as DHF Vector in Kediri District Against Temephos

Dengue Haemorraghic Fever (DHF) becomes health problem in the world. The most number of DHF sufferers in Kediri District in 2016 were in Pare Subdistrict, Ngasem Subdistrict, and Kunjang. However, controlling technique of DHF vector is such as fogging by using active substance of melathion for adult stadium of mosquito and larvasidation by using active substance of temephos for larvae stadium of mosquito. Moreover, resistance of vector against insecticide is global phenomenon, particularly for program management of infectious disease controlling vector and as a singular barrier in the success of vector control chemically. The vector resistance detection can be conducted by using Detection Conventionally through WHO standard method of Susceptibility test in impregnated paper. This research aimed at analyzing detection conventionally the resistance of Aedes aegypti as DHF vector in Kediri District against Malathion and Themepos. This research was True Experiment research and temephos was scattered to the larvae with concentration of 0.01 mg/l, 0.02 mg/l, 0.03 mg/l, and 0.04 mg/l in contact time of 15, 30, 45, and 60 minutes. Data analysis included determination of resistance status by referring to category standard from WHO and analyzing the difference of biota test mortality by using statistical different test of Anova. The result of this research was Aedes aegypti larvae in Kediri District was resistant against temephos with concentration in 0.01 mg/l, 0.02 mg/l, 0.03 mg/l, 0.04 mg/l and there was a significant influence of contact time against the death of Aedes aegypti larvae. Furthermore, suggestion for Health Office in Kediri District was the use of temephos as larvacide was needed in concentration of more than 0.04ml/l. Besides, it was also needed resistance test of Aedes aegypti larvae with concentration of temephos in more than 0.04 mg/l.

Insecticide resistance status of Aedes aegypti and Aedes albopictus mosquitoes in Papua New Guinea

BackgroundAedes aegypti and Ae. albopictus are important vectors of infectious diseases, especially those caused by arboviruses such as dengue, chikungunya and Zika. Aedes aegypti is very well adapted to urban environments, whereas Ae. albopictus inhabits more rural settings. Pyrethroid resistance is widespread in these vectors, but limited data exist from the Southwest Pacific Region, especially from Melanesia. While Aedes vector ecology is well documented in Australia, where incursion of Ae. albopictus and pyrethroid resistance have so far been prevented, almost nothing is known about Aedes populations in neighbouring Papua New Guinea (PNG). With pyrethroid resistance documented in parts of Indonesia but not in Australia, it is important to determine the distribution of susceptible and resistant Aedes populations in this region.MethodsThe present study was aimed at assessing Aedes populations for insecticide resistance in Madang and Port Moresby, located on the north and south coasts of PNG, respectively. Mosquitoes were collected using ovitraps and reared in an insectary. Standard WHO bioassays using insecticide-treated filter papers were conducted on a total of 253 Ae. aegypti and 768 Ae. albopictus adult mosquitoes. Subsets of samples from both species (55 Ae. aegypti and 48 Ae. albopictus) were screened for knockdown resistance mutations in the voltage-sensitive sodium channel (Vssc) gene, the target site of pyrethroid insecticides.ResultsHigh levels of resistance against pyrethroids were identified in Ae. aegypti from Madang and Port Moresby. Aedes albopictus exhibited susceptibility to pyrethroids, but moderate levels of resistance to DDT. Mutations associated with pyrethroid resistance were detected in all Ae. aegypti samples screened. Some genotypes found in the present study had been observed previously in Indonesia. No Vssc mutations associated with pyrethroid resistance were found in the Ae. albopictus samples.ConclusionsTo our knowledge, this is the first report of pyrethroid resistance in Ae. aegypti mosquitoes in PNG. Interestingly, usage of insecticides in PNG is low, apart from long-lasting insecticidal nets distributed for malaria control. Further investigations on how these resistant Ae. aegypti mosquito populations arose in PNG and how they are being sustained are warranted.

Insecticide resistance in Aedes aegypti: An impact from human urbanization?

In the city of Magelang, Indonesia, the distribution of Dengue Haemorhagic Fever (DHF) cases tend to be clustered, ever changing along with human urbanization from 2014 to 2017. Although DHF cases have been less reported in the city of Magelang for the past 5 years, vector control measures by using insecticide space spraying, particularly permethrin, have been continuously performed. Current study aimed to detect kdr mutations associated with pyrethroid resistance in Ae. aegypti and to study possible association between insecticide resistance and DHF case distribution related to human urbanization. The study was a cross sectional study conducted in 3 sub-districts in the city of Magelang, Central Java, Indonesia. Eggs of Ae. aegypti collected from 195 sample households were reared and were tested for resistance to pyrethroids by using PCR. Primers AaSCF1 and AaSCR4, and primers AaSCF7 and AaSCR7 were used in detecting presence of mutation in VGSC IIS6 and IIIS6 gene, respectively. Fragments of amplified DNA were sequenced and were analyzed. Spatio-temporal using Standard Deviational Ellipse (SDE) was performed to obtain mapping of DHF case distribution trends. The total number of DHF case was 380 cases, with the most cases (158) occurred in 2015 and the least cases (66) reported in 2017. DHF case distribution was grouped into several clusters. SDE calculation demonstrated movement of DHF case in the direction to principal arterial road, suggesting link to urbanization. Gene sequencing demonstrated VGSC IIS6 gene mutation (S989P and V1016G) in Ae. aegypti collected from study areas, indicating resistance to permethrin. VGSC IIIS6 gene mutation was not found. Current study concluded that multiple kdr mutations associated with resistance to pyrethroid was detected in Ae. aegypti, and that human urbanization may have a role in the development of such resistance.

Seasonal and geographic variation in insecticide resistance in Aedes aegypti in southern Ecuador

Insecticide resistance (IR) can undermine efforts to control vectors of public health importance. Aedes aegypti is the main vector of resurging diseases in the Americas such as yellow fever and dengue, and recently emerging chikungunya and Zika fever, which have caused unprecedented epidemics in the region. Vector control remains the primary intervention to prevent outbreaks of Aedes-transmitted diseases. In many high-risk regions, like southern Ecuador, we have limited information on IR. In this study, Ae. aegypti IR was measured across four cities in southern Ecuador using phenotypic assays and genetic screening for alleles associated with pyrethroid IR. Bottle bioassays showed significant inter-seasonal variation in resistance to deltamethrin, a pyrethroid commonly used by the Ministry of Health, and alpha-cypermethrin, as well as between-city differences in deltamethrin resistance. There was also a significant difference in phenotypic response to the organophosphate, Malathion, between two cities during the second sampling season. Frequencies of the resistant V1016I genotype ranged from 0.13 to 0.68. Frequencies of the resistant F1534C genotype ranged from 0.63 to 1.0, with sampled populations in Machala and Huaquillas at fixation for the resistant genotype in all sampled seasons. In Machala and Portovelo, there were statistically significant inter-seasonal variation in genotype frequencies for V1016I. Resistance levels were highest in Machala, a city with hyperendemic dengue transmission and historically intense insecticide use. Despite evidence that resistance alleles conferred phenotypic resistance to pyrethroids, there was not a precise correspondence between these indicators. For the F1534C gene, 17.6% of homozygous mutant mosquitoes and 70.8% of heterozygotes were susceptible, while for the V1016I gene, 45.6% homozygous mutants and 55.6% of heterozygotes were susceptible. This study shows spatiotemporal variability in IR in Ae. aegypti populations in southern coastal Ecuador, and provides an initial examination of IR in this region, helping to guide vector control efforts for Ae. aegypti.

Exome-wide association of deltamethrin resistance in Aedes aegypti from Mexico.

Aedes aegypti is the major vector of a number of arboviruses that cause disease in humans. Without vaccines or pharmaceuticals, pyrethroid insecticides remain the major tool for public health protection. Pyrethroid resistance is now widespread. Replacement substitutions in the voltage‐gated sodium channel (vgsc) that reduce the stability of pyrethroid binding account for most of the resistance, but metabolic mechanisms also inactivate pyrethroids. High‐throughput sequencing and the A. aegypti L5 annotated physical map has allowed interrogation of the exome for genes and single‐nucleotide polymorphisms associated with pyrethroid resistance. We exposed females of A. aegypti from Mexico to a deltamethrin discriminating dose to designate them as resistant (active after 1 h) or susceptible (knocked down with no recovery after 4 h). The vgsc on chromosome 3 had the highest association, followed by genes proximal to vgsc. We identified potential detoxification genes located singly (eg HPX8C) or within clusters in chromosome 2 [three esterase clusters, two of cytochrome P450 monooxygenases (CYP)] and chromosome 3 (one cluster of 16 CYP325 and seven CYP9 genes). Deltamethrin resistance in A. aegypti is associated with mutations in the vgsc gene and a large assortment of genes.

Widespread insecticide resistance in Aedes aegypti L. from New Mexico, U.S.A.

BackgroundAedes aegypti mosquitoes are vectors of a variety of emerging viral pathogens, including yellow fever, dengue, chikungunya, and Zika virus. This species has established endemic populations in all cities across southern New Mexico sampled to date. Presently, control of Aedes-borne viruses relies on deployment of insecticides to suppress mosquito populations, but the evolution of insecticide resistance threatens the success of vector control programs. While insecticide resistance is quite common in Ae. aegypti field populations across much of the U.S., the resistance status of this species in populations from New Mexico has not previously been assessed.ResultsFirst, we collected information on pesticide use in cities in southern New Mexico and found that the most commonly used active ingredients were pyrethroids. The use of insecticides with the same mode-of-action over multiple years is likely to promote the evolution of resistance. To determine if there was evidence of resistance in some cities in southern New Mexico, we collected Ae. aegypti from the same cities and established laboratory strains to assess resistance to pyrethroid insecticides and, for a subset of populations, to organophosphate insecticides. F2 or F4 generation mosquitoes were assessed for insecticide resistance using bottle test bioassays. The majority of the populations from New Mexico that we analyzed were resistant to the pyrethroids permethrin and deltamethrin. A notable exception to this trend were mosquitoes from Alamogordo, a city that did not report using pyrethroid insecticides for vector control. We screened individuals from each population for known knock down resistance (kdr) mutations via PCR and found a strong association between the presences of the F1534C kdr mutation in the para gene of Ae. aegypti (homologue to F1534C in Musca domestica L.) and pyrethroid resistance.ConclusionHigh-level pyrethroid resistance is common in Ae. aegypti from New Mexico and geographic variation in such resistance is likely associated with variation in usage of pyrethroids for vector control. Resistance monitoring and management is recommended in light of the potential for arbovirus outbreaks in this state. Also, alternative approaches to mosquito control that do not involve insecticides should be explored.

Insecticide resistance in Aedes albopictus Skuse from sub-Himalayan districts of West Bengal, India

Dengue is one of the most rapidly spreading infectious diseases prevalent throughout the tropical and sub-tropical regions of the world. In absence of specific medications and vaccines, the sole method of disease prevention relies on vector control mainly using insecticides. But with the advent of Insecticide resistance, worldwide vector control programs are facing failure. In this study, eleven different Ae. albopictus population from sub-Himalayan districts of West Bengal, India were investigated as per WHO protocols to find out the current status of insecticide susceptibility against DDT, permethrin and propoxur. Also the role of three insecticide detoxifying enzymes underlying observed resistance was investigated through quantitative and synergistic assays to unveil the mechanism of insecticide resistance. It was found that majority of studied populations were resistant to 4% DDT. Two populations, namely Alipurduar (APD) and Jalpaiguri (JPG) were severely resistant to 0.75% permethrin, whereas only JPG population was found to exhibit severe resistance against 0.1% propoxur. Moreover, the involvement of detoxifying enzymes was also noted in conferring resistance against DDT and Permethrin. This study indicates the inefficacy of DDT in controlling Ae. albopictus populations in the study region. This study may help in implementation of an efficient vector control and insecticide resistance management strategies.

Homologs of Human Dengue-Resistance Genes, FKBP1B and ATCAY, Confer Antiviral Resistance in Aedes aegypti Mosquitoes.

Dengue virus (DENV) is transmitted by mosquitoes and is a major public health concern. The study of innate mosquito defense mechanisms against DENV have revealed crucial roles for the Toll, Imd, JAK-STAT, and RNAi pathways in mediating DENV in the mosquito. Often overlooked in such studies is the role of intrinsic cellular defense mechanisms that we hypothesize to work in concert with the classical immune pathways to affect organismal defense. Our understanding of the molecular interaction of DENV with mosquito host cells is limited, and we propose to expand upon the recent results from a genome-scale, small interfering RNA (siRNA)-based study that identified mammalian host proteins associated with resistance to dengue/West Nile virus (DENV/WNV) infection. The study identified 22 human DENV/WNV resistance genes (DVR), and we hypothesized that a subset would be functionally conserved in Aedes aegypti mosquitoes, imparting cellular defense against flaviviruses in this species. We identified 12 homologs of 22 human DVR genes in the Ae. aegypti genome. To evaluate their possible role in cellular resistance/antiviral defense against DENV, we used siRNA silencing targeted against each of the 12 homologs in an Ae. aegypti cell line (Aag2) infected with DENV2 and identified that silencing of the two candidates, AeFKBP1 and AeATCAY, homologs of human FKBP1B and ATCAY, were associated with a viral increase. We then used dsRNA to silence each of the two genes in adult mosquitoes to validate the observed antiviral functions in vivo. Depletion of AeFKBP1 or AeATCAY increased viral dissemination through the mosquito at 14 days post-infection. Our results demonstrated that AeFKBP1 and AeATCAY mediate resistance to DENV akin to what has been described for their homologs in humans. AeFKBP1 and AeATCAY provide a rare opportunity to elucidate a DENV-resistance mechanism that may be evolutionarily conserved between humans and Ae. aegypti.

Resistance of Aedes as a Vectors Potential for Dengue Hemorrhagic Fever (DHF) in Semarang City, Indonesia

Dengue Hemorrhagic Fever (DHF) is a significant health problem in Semarang, Indonesia. A Certain type of insecticides has been widely applied beginning in the last decade as an effort to control the mosquito vectors of dengue virus. This practice could lead to increased resistance in mosquito populations toward these types of insecticides. This research aimed to describe the resistance status of Aedes sp. populations in Semarang. A cross-sectional design study was conducted in 2015, with Aedes sp. populations sampled in several villages of Semarang. Field strains of Aedes sp. eggs were collected using ovitraps and larvae from entomological surveys. Mosquito adults were raised from the collected eggs and larvae under standard conditions and used for biochemical assays. ELISA examined Aedes sp . resistance status. The results showed that there was monooxygenase activity in Aedes sp. populations. In quantitative terms, 77.8% of mosquito samples showed an Optical Density (OD) more than the cut-off point (0.165). Resistance to synthetic pyrethroid insecticide in Aedes sp. mosquitoes population in Semarang may be caused by the mechanism of monooxygenase detoxification enzymes in particular. This case indicated that Aedes sp. has a high capacity as a vector to transmit the dengue virus in Semarang.