Dataset Information

Permethrin Resistance in Aedes aegypti Affects Aspects of Vectorial Capacity.

ABSTRACT: 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.

SUBMITTER: Chen TY

PROVIDER: S-EPMC7830706 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Permethrin Resistance in Aedes aegypti Affects Aspects of Vectorial Capacity.

Chen Tse-Yu TY Smartt Chelsea T CT Shin Dongyoung D

Insects 20210114 1

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</ ...[more]

PMID: 33466960

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Project description:Aedes aegypti poses a serious risk to human health due to its wide global distribution, high vector competence for several arboviruses, frequent human biting, and ability to thrive in urban environments. Pyrethroid insecticides remain the primary means of controlling adult A. aegypti populations during disease outbreaks. As a result of decades of use, pyrethroid resistance is a global problem. Cytochrome P450 monooxygenase (CYP)-mediated detoxification is one of the primary mechanisms of pyrethroid resistance. However, the specific CYP(s) responsible for resistance have not been unequivocally determined. We introgressed the resistance alleles from the resistant A. aegypti strain, Singapore (SP), into the genetic background of the susceptible ROCK strain. The resulting strain (CKR) was congenic to ROCK. Our primary goal was to determine which CYPs in SP are linked to resistance. To do this, we first determined which CYPs overexpressed in SP are also overexpressed in CKR, with the assumption that only the CYPs linked to resistance will be overexpressed in CKR relative to ROCK. Next, we determined whether any of the overexpressed CYPs were genetically linked to resistance (cis-regulated) or not (trans-regulated). We found that CYP6BB2, CYP6Z8, CYP9M5 and CYP9M6 were overexpressed in SP as well as in CKR. Based on the genomic sequences and polymorphisms of five single copy CYPs (CYP4C50, 6BB2, 6F2, 6F3 and 6Z8) in each strain, none of these genes were linked to resistance, except for CYP6BB2, which was partially linked to the resistance locus. Hence, overexpression of these four CYPs is due to a trans-regulatory factor(s). Knowledge on the specific CYPs and their regulators involved in resistance is critical for resistance management strategies because it aids in the development of new control chemicals, provides information on potential environmental modulators of resistance, and allows for the detection of resistance markers before resistance becomes fixed in the population.

Project description:Pyrethroids are one of the few classes of insecticides available to control Aedes aegypti, the major vector of dengue, chikungunya, and Zika viruses. Unfortunately, evolving mechanisms of pyrethroid resistance in mosquito populations threaten our ability to control disease outbreaks. Two common pyrethroid resistance mechanisms occur in Ae. aegypti: 1) knockdown resistance, which involves amino acid substitutions at the pyrethroid target site-the voltage-gated sodium channel (VGSC)-and 2) enhanced metabolism by detoxification enzymes. When a heterogeneous population of mosquitoes is exposed to pyrethroids, different responses occur. During exposure, a proportion of mosquitoes exhibit immediate knockdown, whereas others are not knocked-down and are designated knockdown resistant (kdr). When these individuals are removed from the source of insecticide, the knocked-down mosquitoes can either remain in this status and lead to dead or recover within a few hours. The proportion of these phenotypic responses is dependent on the pyrethroid concentration and the genetic background of the population tested. In this study, we sequenced and performed pairwise genome comparisons between kdr, recovered, and dead phenotypes in a pyrethroid-resistant colony from Tapachula, Mexico. We identified single-nucleotide polymorphisms (SNPs) associated with each phenotype and identified genes that are likely associated with the mechanisms of pyrethroid resistance, including detoxification, the cuticle, and insecticide target sites. We identified high association between kdr and mutations at VGSC and moderate association with additional insecticide target site, detoxification, and cuticle protein coding genes. Recovery was associated with cuticle proteins, the voltage-dependent calcium channel, and a different group of detoxification genes. We provide a list of detoxification genes under directional selection in this field-resistant population. Their functional roles in pyrethroid metabolism and their potential uses as genomic markers of resistance require validation.

Project description:The rapid expansion of Zika virus (ZIKV), following the recent outbreaks of Chikungunya virus, overwhelmed the public health infrastructure in many countries and alarmed many in the scientific community. Aedes aegypti (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) have previously been incriminated as the vectors of these pathogens in addition to dengue virus. In our study, we challenged low generation Ae. aegypti (Chiapas, Mexico) and Ae. albopictus (North Carolina, Mississippi), with three strains of ZIKV, Puerto Rico (GenBank: KU501215), Honduras (GenBank: KX694534), and Miami (GenBank: MF988743). Following an oral challenge with 107.5 PFU/ml of the Puerto Rico strain, we observed high infection and dissemination rates in both species (95%). We report estimated transmission rates for both species (74 and 33%, for Ae. aegypti (L.) (Diptera: Culicidae) and Ae. albopictus (Skuse) (Diptera: Culicidae), respectively), and the presence of a probable salivary gland barrier in Ae. albopictus to Zika virus. Finally, we calculated vectorial capacity for both species and found that Ae. albopictus had a slightly lower vectorial capacity when compared with Ae. aegypti.Second Language Abstract: La rápida expansión del virus Zika, poco después de las epidemias de chikungunya, rebaso la infraestructura de salud pública en muchos países y sorprendió a muchos en la comunidad científica. Notablemente, Aedes aegypti y Aedes albopictus transmiten estos patógenos además del virus del dengue. En este estudio se expusieron con tres cepas americanas de virus Zika a grupos de Aedes aegypti y Aedes albopictus de generación reciente. Encontramos altos porcentajes de infección y diseminación en ambas especies (95%). Se reporta, la transmisión viral en ambas especies (74 y 33%, para Aedes aegypti and Aedes albopictus, respectivamente) y una probable barrera a nivel de glándulas salivarías. Finalmente, calculamos la capacidad vectorial para ambas especies.

Project description:Recent outbreaks of locally transmitted dengue and Zika viruses in Florida have placed more emphasis on integrated vector management plans for Aedes aegypti (L.) and Aedes albopictus Skuse. Adulticiding, primarily with pyrethroids, is often employed for the immediate control of potentially arbovirus-infected mosquitoes during outbreak situations. While pyrethroid resistance is common in Ae. aegypti worldwide and testing is recommended by CDC and WHO, resistance to this class of products has not been widely examined or quantified in Florida. To address this information gap, we performed the first study to quantify both pyrethroid resistance and genetic markers of pyrethroid resistance in Ae. aegypti and Ae. albopictus strains in Florida. Using direct topical application to measure intrinsic toxicity, we examined 21 Ae. aegypti strains from 9 counties and found permethrin resistance (resistance ratio (RR) = 6-61-fold) in all strains when compared to the susceptible ORL1952 control strain. Permethrin resistance in five strains of Ae. albopictus was very low (RR<1.6) even when collected from the same containers producing resistant Ae. aegypti. Characterization of two sodium channel kdr alleles associated with pyrethroid-resistance showed widespread distribution in 62 strains of Ae. aegypti. The 1534 phenylalanine to cysteine (F1534C) single nucleotide polymorphism SNP was fixed or nearly fixed in all strains regardless of RR. We observed much more variation in the 1016 valine to isoleucine (V1016I) allele and observed that an increasing frequency of the homozygous V1016I allele correlates strongly with increased RR (Pearson corr = 0.905). In agreement with previous studies, we observed a very low frequency of three kdr genotypes, IIFF, VIFF, and IIFC. In this study, we provide a statewide examination of pyrethroid resistance, and demonstrate that permethrin resistance and the genetic markers for resistance are widely present in FL Ae. aegypti. Resistance testing should be included in an effective management program.

Dataset Information

Permethrin Resistance in Aedes aegypti Affects Aspects of Vectorial Capacity.

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Permethrin Resistance in <i>Aedes aegypti</i> Affects Aspects of Vectorial Capacity.

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