Impact of the V410L kdr mutation and co-occurring genotypes at kdr sites 1016 and 1534 in the VGSC on the probability of survival of the mosquito Aedes aegypti (L.) to Permanone in Harris County, TX, USA

Impact of field evolved resistance on biological parameters of non-targeted Aedes aegypti populations

The yellow fever mosquito, Aedes aegypti L., known for transmitting viruses causing yellow fever, dengue, chikungunya, and Zika fever, presents a substantial risk to global human health. The development of insecticide resistance in disease vectors has become a significant problem in Ae. aegypti. Monitoring insecticide resistance is essential for resistance management in Ae. aegypti. This study involved the collection of Ae. aegypti populations from four important cotton-growing regions in southern Punjab, Pakistan, for resistance monitoring over a two-year period (2021-2022). This study also assessed the impact of insecticide resistance on biological parameters of Ae. aegypti. Moderate-to-high levels of resistance were observed against all the tested insecticides viz., chlorpyrifos, chlorfenapyr, deltamethrin, flonicamid, spirotetramat, and spinetoram. However, compared to the Lab-susceptible population, higher levels of resistance to buprofezin (59.03-84.40) and imidacloprid (68.49-100.01) were found in all populations. This high resistance can be attributed to increased use of these two insecticides in cotton fields, as compared to other insecticides. In the lab-susceptible population, higher values for the intrinsic rate of increase (r) and the net reproductive rate (R0) i.e., 0.20 per day and 23.24 offspring/female were observed, respectively. This was also validated by population projection data where more than 2.5-fold adults (1,020,361.80 individuals) were calculated in the Lab-susceptible population as compared to the most resistant populations. Sublethal exposure to insecticides may induce physiological or biochemical changes in organisms, subsequently influencing the biological traits. Resistance monitoring provides essential guidance before launching a successful chemical-based vector management program.

Omics Approaches in Understanding Insecticide Resistance in Mosquito Vectors

In recent years, the emergence of insecticide resistance has been a major challenge to global public health. Understanding the molecular mechanisms of this phenomenon in mosquito vectors is paramount for the formulation of effective vector control strategies. This review explores the current knowledge of insecticide resistance mechanisms through omics approaches. Genomic, transcriptomic, proteomic, and metabolomics approaches have proven crucial to understand these resilient vectors. Genomic studies have identified multiple genes associated with insecticide resistance, while transcriptomics has revealed dynamic gene expression patterns in response to insecticide exposure and other environmental stimuli. Proteomics and metabolomics offer insights into protein expression and metabolic pathways involved in detoxification and resistance. Integrating omics data holds immense potential to expand our knowledge on the molecular basis of insecticide resistance in mosquitoes via information obtained from different omics platforms to understand regulatory mechanisms and differential expression of genes and protein, and to identify the transcription factors and novel molecules involved in the detoxification of insecticides. Eventually, these data will help construct predictive models, identify novel strategies, and develop targeted interventions to control vector-borne diseases.

The V410L kdr allele in the VGSC confers higher levels of field resistance to permethrin in urban mosquito populations of Aedes aegypti (L.)

BACKGROUND

Females of Aedes aegypti transmit emerging arboviruses including Zika, dengue, yellow fever, and chikungunya. Control of these adult mosquitoes heavily relies on synthetic insecticides, including pyrethroids. However, insecticide resistance development in populations poses a significant challenge to vector control, particularly from knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC), the target of pyrethroids. This study investigated the field efficacy of Permanone, a pyrethroid-based insecticide, against Ae. aegypti by assessing the impact of three common kdr mutations (V410L, V1016I, F1534C) on mosquito survival under a real operational mosquito control scenario, by quantifying the pesticide delivered in the field.

RESULTS

Field cage tests (FCTs) were conducted while conducting a realistic mosquito control application. Female mosquitoes from six operational areas from Harris County, TX, USA were exposed to Permanone delivered with a handheld sprayer. Permanone deposited near the cages was estimated from aluminum boats placed in the field during FCTs using gas chromatography-mass spectrometry (GC-MS). Mortality rates were recorded, and individual mosquitoes were genotyped for kdr mutations. A probit regression model was used to analyze the factors influencing mosquito survivorship. As the distance from the application source route increased, the amount of Permanone deposited decreased, resulting in higher survivorship frequency of Ae. aegypti females with the triple-resistant kdr genotype (LL/II/CC). The L allele at the 410-site significantly contributed to an increased resistance level when co-occurring with other kdr mutations.

CONCLUSION

This study linked the survival probabilities of mosquitoes with different kdr genotypes, and the amount of pesticide they received in the field. Pesticide quantification, control efficacy results and genotyping allowed us to empirically determine the impact of genotypic resistance on vector control in the field. © 2024 Society of Chemical Industry.

Monitoring of pyrethroid resistance in Aedes aegypti: first report of double and triple kdr mutations in Buenos Aires Province

BACKGROUND

Dengue is an emerging disease in Argentina due to the colonization of Aedes aegypti, the mosquito vector. Buenos Aires Province is the biggest and most populated district in Argentina, suffering dengue outbreaks of growing magnitude. During epidemic periods, pyrethroid insecticides are used in this country to control adult mosquitoes. Pyrethroid resistance in dengue vectors has been reported worldwide, making it necessary to implement resistance management strategies. The voltage-gated sodium channel is the target site of pyrethroids. Mutations in the gene encoding this protein, called kdr mutations, are usually the molecular cause of pyrethroid resistance in insects. In Ae. aegypti from the Americas, three kdr substitutions were described: V410L, V1016I, and F1534C. The diagnostic of kdr mutations is recommended for the early detection of pyrethroid resistance as well as the consequent planning of evidence-based control policies.

METHODS

We distributed ovitraps across 16 localities in Buenos Aires Province, collecting 22,123 eggs. A total of 522 mosquitoes were genotyped in positions 1016 and 1534 of voltage-gated channel using multiplex high-resolution melting and/or TaqMan probe methods. A subset of 449 samples was also genotyped by a singleplex high-resolution melting method developed ad hoc and/or Sanger sequencing.

RESULTS

We have documented, for the first time to our knowledge in the central region of Argentina, the presence of the 1016Ikdr + 1534Ckdr allele. Additionally, our study reports the first identification of the V410L mutation in central Argentina. These results underscore a growing trend of pyrethroid resistance in Ae. aegypti, fueled by the widespread use of these insecticides.

CONCLUSIONS

We detected 1016Ikdr + 1534Ckdr and 410Lkdr mutations in central Argentina for the first time and improved the processivity and accuracy of kdr genotyping methods. The results are both a tool for resistance monitoring and a sign of alarm to direct efforts towards finding sustainable methods for vector control to complement or replace pyrethroids. Joint efforts between academia and authorities to develop and implement public policies for vector control are a productive way to transfer scientific results for their application in public health.

Assessing pyrethroid resistance in Aedes aegypti from Cordoba Colombia: Implications of kdr mutations

Resistance to insecticides is one of the great challenges that vector control programs must face. The constant use of pyrethroid-type insecticides worldwide has caused selection pressure in populations of the Aedes aegypti vector, which has promoted the emergence of resistant populations. The resistance mechanism to pyrethroid insecticides most studied to date is target-site mutations that desensitize the voltage-gated sodium channel (VGSC) of the insect to the action of pyrethroids. In the present study, susceptibility to the pyrethroid insecticides permethrin, lambda-cyhalothrin, and deltamethrin was evaluated in fourteen populations from the department of Córdoba, Colombia. The CDC bottle bioassay and WHO tube methods were used. Additionally, the frequencies of the F1534C, V1016I, and V410L mutations were determined, and the association of resistance with the tri-locus haplotypes was examined. The results varied between the two techniques used, with resistance to permethrin observed in thirteen of the fourteen populations, resistance to lambda-cyhalothrin in two populations, and susceptibility to deltamethrin in all the populations under study with the CDC method. In contrast, the WHO method showed resistance to the three insecticides evaluated in all populations. The frequencies of the mutated alleles ranged from 0.05-0.43 for 1016I, 0.94-1.0 for 1534C, and 0.01-0.59 for 410L. The triple homozygous mutant CIL haplotype was associated with resistance to all three pyrethroids evaluated with the WHO bioassay, while with the CDC bioassay, it was only associated with resistance to permethrin. This study highlights the importance of implementing systematic monitoring of kdr mutations, allowing resistance management strategies to be dynamically adjusted to achieve effective control of Aedes aegypti.

First detection of V410L kdr mutation in Aedes aegypti populations of Argentina supported by toxicological evidence

BACKGROUND

Aedes aegypti (L.) is the main vector of dengue, yellow fever, Zika, and chikungunya viruses in many parts of the world, impacting millions of people worldwide each year. Insecticide-based interventions have been effective in controlling Aedes mosquito populations for several years, but in recent times, resistance to these compounds has developed, posing a global threat to the control of this mosquito.

METHODS

Ovitraps were used to collect A. aegypti eggs in the cities of Tartagal and San Ramón de la Nueva Orán (Salta), Puerto Iguazú (Misiones), and Clorinda (Formosa). World Health Organization (WHO)-impregnated papers with the discriminating concentration (DC) of permethrin, 5X, 10X and pirimiphos methyl were used for the toxicological bioassays. We also genotyped each sample for the three kdr single nucleotide polymorphisms (SNP): V410L, V1016I, and F1534C in individual TaqMan quantitative PCR (qPCR) reactions.

RESULTS

All investigated A. aegypti populations were highly resistant to permethrin, as the mortality percentage with the permethrin 10×DC remained below 98%. However, all populations were 100% susceptible to pirimiphos-methyl. Kdr genotyping demonstrated the presence of the V410L mutation for the first time in Argentina in all the populations studied. A prevalence of the triple mutant genotype (LL + II + CC) was observed in the northeastern cities of Clorinda (83.3%) and Puerto Iguazú (55.6%).

CONCLUSIONS

This study demonstrates for the first time the presence and intensity of resistance to permethrin in different populations from Argentina, and correlates the observed phenotype with the presence of kdr mutations (genotype).

Recent advances in the study of knockdown resistance mutations in Aedes mosquitoes with a focus on several remarkable mutations

The Aedes mosquito, which transmits the dengue fever virus and other viruses, has acquired resistance to pyrethroid insecticides in a naturally selective manner. Massive use of insecticides has led to the worldwide expansion of resistant populations. The major factor in pyrethroid resistance is knockdown resistance (kdr) caused by amino acid mutation(s) in the voltage-gated sodium channel, which is the target site of this insecticide group. Some kdr mutations can lead to a dramatic increase in resistance, and multiple mutations can increase the level of pyrethroid resistance by 10 to several-hundred. In this review, we summarize the kdr identified in Aedes mosquitoes with a focus on the recent advances in the study of kdr.

Potential of MALDI-TOF MS biotyping to detect deltamethrin resistance in the dengue vector Aedes aegypti

Insecticide resistance in mosquitoes is spreading worldwide and represents a growing threat to vector control. Insecticide resistance is caused by different mechanisms including higher metabolic detoxication, target-site modification, reduced penetration and behavioral changes that are not easily detectable with simple diagnostic methods. Indeed, most molecular resistance diagnostic tools are costly and labor intensive and then difficult to use for routine monitoring of insecticide resistance. The present study aims to determine whether mosquito susceptibility status against the pyrethroid insecticides (mostly used for mosquito control) could be established by the protein signatures of legs and/or thoraxes submitted to MALDI-TOF Mass Spectrometry (MS). The quality of MS spectra for both body parts was controlled to avoid any bias due to unconformity protein profiling. The comparison of MS profiles from three inbreeds Ae. aegypti lines from French Guiana (IRF, IR03, IR13), with distinct deltamethrin resistance genotype / phenotype and the susceptible reference laboratory line BORA (French Polynesia), showed different protein signatures. On both body parts, the analysis of whole protein profiles revealed a singularity of BORA line compared to the three inbreeding lines from French Guiana origin, suggesting that the first criteria of differentiation is the geographical origin and/or the breeding history rather than the insecticide susceptibility profile. However, a deeper analysis of the protein profiles allowed to identify 10 and 11 discriminating peaks from leg and thorax spectra, respectively. Among them, a specific peak around 4870 Da was detected in legs and thoraxes of pyrethroid resistant lines compared to the susceptible counterparts hence suggesting that MS profiling may be promising to rapidly distinguish resistant and susceptible phenotypes. Further work is needed to confirm the nature of this peak as a deltamethrin resistant marker and to validate the routine use of MS profiling to track insecticide resistance in Ae. aegypti field populations.

Kdr genotyping and the first report of V410L and V1016I kdr mutations in voltage-gated sodium channel gene in Aedes aegypti (Diptera: Culicidae) from Iran

BACKGROUND

Aedes aegypti is the main vector of arboviral diseases worldwide. The species invaded and became established in southern Iran in 2020. Insecticide-based interventions are primarily used for its control. With insecticide resistance widespread, knowledge of resistance mechanisms is vital for informed deployment of insecticidal interventions, but information from Iranian Ae. aegypti is lacking.

METHODS

Fifty-six Ae. aegypti specimens were collected from the port city of Bandar Lengeh in Hormozgan Province in the South of Iran in 2020 and screened for kdr mutations. The most common kdr mutations in Latin America and Asia (V410L, S989P, V1016G/I and F1534C), especially when present in combinations, are highly predictive of DDT and pyrethroid resistance were detected. Phylogenetic analyses based on the diversity of S989P and V1016G/I mutations were undertaken to assess the phylogeography of these kdr mutations.

RESULTS

Genotyping all four kdr positions of V410L, S989P, V1016G/I and F1534C revealed that only 16 out of the 56 (28.57%) specimens were homozygous wild type for all kdr mutation sites. Six haplotypes including VSVF (0.537), VSVC (0.107), LSVF (0.016), LSIF (0.071), VPGC (0.257) and LPGC (0.011) were detected in this study. For the first time, 11 specimens harbouring the V410L mutation, and 8 samples with V1016I mutation were found. V410L and V1016I were coincided in 8 specimens. Also, six specimens contained 1016G/I double mutation which was not reported before.

CONCLUSIONS

The relatively high frequency of these kdr mutations in Iranian Ae. aegypti indicates a population exhibiting substantial resistance to pyrethroid insecticides, which are used widely in control operations and household formulations. The detection of the 410L/1016I kdr mutant haplotype in Iranian Ae. aegypti suggests possible convergence of invasive populations from West Africa or Latin America. However, as Iran has very limited maritime/air connections with those African countries, a Latin American origin for the invasive Ae. aegypti in Iran is more plausible.

Automated analysis of feeding behaviors of females of the mosquito Aedes aegypti using a modified flyPAD system

Mosquitoes present a global health challenge due to their ability to transmit human and animal pathogens upon biting and blood feeding. The investigation of tastants detected by mosquitoes and their associated feeding behaviors is needed to answer physiological and ecological questions that could lead to novel control methods. A high-throughput system originally developed for research in fruit flies feeding behavior, the flyPAD, was adapted and tested for behaviors associated with the interaction or consumption of liquid diets offered to females of the mosquito Aedes aegypti Liverpool strain. Females were given water, sucrose solution and sheep blood in choice and non-choice assays. The volume ingested was evaluated with fluorescein. The placement of the system on a heated surface allowed blood consumption, and without females puncturing a membrane. The flyPAD system recorded nine feeding behavioral variables, of which the number of sips and number of activity bouts correlated with meal volume ingested for both sucrose solution and blood. The adaptation to mosquitoes of the flyPAD system differentiated feeding behavior variables between two feeding deterrents, capsaicin, and caffeine. The flyPAD has potential to quickly assess diverse tastants in both sucrose and blood and may contribute to characterizing more precisely their mode of action.

Genetic structure and kdr mutations in Aedes aegypti populations along a road crossing the Amazon Forest in Amapá State, Brazil

Insecticide resistance in Aedes aegypti poses a significant threat to disease control. One form of resistance, caused by kdr mutations in the NaV gene, hinders vector control efforts in Brazil. Despite genetic differences typically accumulating among isolated populations, this mosquito can actively and passively disperse through human transportation. Our study investigated the genetic structure and spread of kdr mutations in Ae. aegypti populations across six localities in Amapá State, Brazil, within the Amazonian Forest. Using 12 microsatellite loci and qPCR methods, we assessed genetic structure and identified three common kdr mutations (V410L, V1016I, and F1534C). High prevalence of kdr alleles was observed in all localities, indicating widespread distribution in Amapá State. Microsatellite analysis revealed differentiation among mosquito populations, dividing them into two distinct clusters supported by Bayesian and DAPC analyses. Oiapoque, located along the northern border with French Guiana, exhibited the highest kdr frequencies and genetic differentiation compared to other localities. Our findings suggest genetic structure in Ae. aegypti populations in Amapá State, with some passive gene flow between clusters. The study underscores the need for continuous surveillance of Ae. aegypti populations to monitor the spread of insecticide resistance and inform effective vector control strategies.

Evaluation of field resistance in field-collected mosquito Culex quinquefasciatus Say through quantification of ULV permethrin/PBO formulation in field bioassays

BACKGROUND

Pyrethroids are among the most applied adulticides worldwide to control mosquito vectors for prevention of arboviral diseases transmission. However, pesticide resistance development in a mosquito population could lead to decreased control efficacy. While most studies investigate the resistant genotype (i.e. kdr, CYP450, etc.) as explanatory variables, few field efficacy studies have measured pesticide quantities deposited at different distances from the sprayer in association with observed mosquito mortality. The current study determined field delivered amounts of an applied ULV permethrin/PBO formulation (31% permethrin + 66% piperonyl butoxide) by GC/MS and estimated practical resistance ratios using caged mosquito females.

RESULTS

For field samples, the extraction method recovered 78 ± 3.92-108 ± 8.97% of the permethrin/PBO formulation when utilizing the peaks of PBO from GC/MS to estimate the concentrations of adulticide deposited near the mosquito cages. The field bioassay showed that the spatial distribution of permethrin/PBO formulation was heterogeneous among three pseudo-replicates within the same distance. Within the quantifiable permethrin/PBO range of 15.7-51.4 ng/cm2 , field-collected mosquito mortalities started at 64% and linearly increased reaching 100% only in two areas, while all Sebring susceptible mosquitoes died. The field LC95 resistance ratio (RR) of F0 Cx. quinquefasciatus ranged from 2.65-3.51, falling within the 95% CI of RR95 estimated by laboratory vial assays. Tests with and without PBO indicated P450's enzymes contributed to field resistance.

CONCLUSION

Results showed the suitability of the collection and quantification method to estimate the field resistance ratio at the applied pesticide rate. Pesticide quantification would also allow the association of the known frequencies of resistance mechanisms (e.g. kdr, CYP450) with field mortalities to estimate the resistance level conferred by such mechanisms. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Entomological surveillance on Aedes aegypti during covid 19 period in Cape Coast, Ghana: Risk of arboviral outbreaks, multiple insecticide resistance and distribution of F1534C, V410L and V1016I kdr mutations

BACKGROUND

The study assessed the risk of transmission of Aedes-borne arboviruses in a community at Cape Coast during the Covid-19 restriction period in 2020 based on entomological indices. The spatial distribution of insecticide resistance was also assessed in Ae. aegypti population from Cape Coast.

METHODS

Three larval indices were calculated from a household larval survey in 100 randomly selected houses. WHO susceptibility bioassay was performed on female adult Ae. aegypti that were reared from the larvae collected from household containers and other receptacles located outside houses against four insecticides. The mosquitoes were also screened for F1534C, V1016I, and V410L kdr mutations.

RESULTS

The estimated larval indices in the study community were House index- 34%, Container index- 22.35%, and Breteau index- 2.02. The mosquito population was resistant to Deltamethrin (0.05%), DDT (4%), Fenitrothion (1%), and Bendiocarb (0.1%). A triple kdr mutation, F1534C, V410L and V1016I were detected in the mosquito population.

CONCLUSION

The study found the risk of an outbreak of Aedes-borne diseases lower in the covid-19 lockdown period than before the pandemic period. The low risk was related to frequent clean-up exercises in the community during the Covid-19 restriction period. Multiple insecticide resistance couple with three kdr mutations detected in the study population could affect the effectiveness of control measures, especially in emergency situations. The study supports sanitation improvement as a tool to control Ae. aegypti and could complement insecticide-based tools in controlling this vector.

Association of 410L, 1016I and 1534C kdr mutations with pyrethroid resistance in Aedes aegypti from Ouagadougou, Burkina Faso, and development of a one-step multiplex PCR method for the simultaneous detection of 1534C and 1016I kdr mutations

BACKGROUND

Since 2000, Burkina Faso has experienced regular dengue cases and outbreaks, making dengue an increasingly important health concern for the country. Previous studies in Burkina Faso reported that resistance of Aedes aegypti to pyrethroid insecticides was associated with the F1534C and V1016I kdr mutations. The current study reports high resistance of Ae. aegypti populations to pyrethroid insecticides, likely supported by mutations in the voltage-gated sodium channel, here evidenced by genotyping the kdr SNPs V410L, V1016I and F1534C. We also describe a new multiplex PCR-based diagnostic of F1534C and V1016I kdr SNPs.

METHODS

Larvae of Ae. aegypti were collected from three health districts of Ouagadougou in 2018. The resistance status of Ae. aegypti to permethrin (15 μg/ml) and deltamethrin (10 μg/ml) was tested using bottles and to malathion (5%) using WHO tube tests. All bioassays used 1-h exposure and mortality recorded 24 h post-exposure. Bioassay results were interpreted according to WHO thresholds for resistance diagnosis. The kdr mutations were screened using AS-PCR and TaqMan methods in exposed and non-exposed Aedes mosquitoes.

RESULTS

Females from all health districts were resistant to permethrin and deltamethrin (< 20% mortality) but were fully susceptible to 5% malathion. The F1534C and V1016I kdr mutations were successfully detected using a newly developed multiplex PCR in perfect agreement with TaqMan method. The 1534C/1016I/410L haplotype was correlated with permethrin resistance but not with deltamethrin resistance; however, the test power was limited by a low frequency of dead individuals in deltamethrin exposure.

CONCLUSIONS

Resistance to pyrethroid insecticides is associated with kdr mutant haplotypes, while the absence of substantial resistance to malathion suggests that it remains a viable option for dengue vector control in Ouagadougou.