Permethrin resistance is widespread in Aedes aegypti (L.), the main dengue, zika, and chikungunya virus vector in Latin America and the Caribbean. A common mechanism of resistance to pyrethroids-knockdown resistance (kdr)-is conferred through mutations in the insect's voltage-dependent sodium channel. In this mosquito, around 10 replacement substitutions in the voltage-gated sodium channel gene (vgsc) have been reported in pyrethroid-resistant strains. Two of these mutations, named Ile1,016 and Cys1,534, are widespread in mosquito populations from Latin America and the Caribbean. This study assessed the levels of permethrin resistance and the frequency of two kdr mutations in eight Ae. aegypti populations collected in Puerto Rico in 2013. Permethrin resistance factors ranged from 33-214-fold relative to the New Orleans reference strain. The frequency of kdr mutation Ile1,016 ranged from 0.65 to fixation (1.0), and for Cys1,534 frequencies varied from 0.8 to fixation. Alarmingly, two populations-Carolina and Caguas-reached fixation at both loci. Our results suggest that permethrin effectiveness for Ae. aegypti control is compromised in these collections from Puerto Rico.

Segmental identity along the anteroposterior axis of bilateral animals is specified by Hox genes. These genes encode transcription factors, harboring the conserved homeodomain and, generally, a YPWM motif, which binds Hox cofactors and increases Hox transcriptional specificity in vivo. Here we derive synthetic Drosophila Antennapedia genes, consisting only of the YPWM motif and homeodomain, and investigate their functional role throughout development. Synthetic peptides and full-length Antennapedia proteins cause head-to-thorax transformations in the embryo, as well as antenna-to-tarsus and eye-to-wing transformations in the adult, thus converting the entire head to a mesothorax. This conversion is achieved by repression of genes required for head and antennal development and ectopic activation of genes promoting thoracic and tarsal fates, respectively. Synthetic Antennapedia peptides bind DNA specifically and interact with Extradenticle and Bric-à-brac interacting protein 2 cofactors in vitro and ex vivo. Substitution of the YPWM motif by alanines abolishes Antennapedia homeotic function, whereas substitution of YPWM by the WRPW repressor motif, which binds the transcriptional corepressor Groucho, allows all proteins to act as repressors only. Finally, naturally occurring variations in the size of the linker between the homeodomain and YPWM motif enhance Antennapedia repressive or activating efficiency, emphasizing the importance of linker size, rather than sequence, for specificity. Our results clearly show that synthetic Antennapedia genes are functional in vivo and therefore provide powerful tools for synthetic biology. Moreover, the YPWM motif is necessary-whereas the entire N terminus of the protein is dispensable-for Antennapedia homeotic function, indicating its dual role in transcriptional activation and repression by recruiting either coactivators or corepressors.Hox specificity | synthetic genes | homeotic transformations | antenna-to-tarsus transformation

Aedes aegypti (L.) is the primary vector of the viruses that cause dengue, Zika, and chikungunya, for which effective vaccines and drugs are still lacking. Current strategies for suppressing arbovirus outbreaks based on insecticide use pose a challenge because of the rapid increase in resistance. The widespread and excessive use of pyrethroid-based insecticides has created a large selection pressure for a kdr-type resistance, caused by mutations in the para gene of the voltage-gated sodium channel (vgsc). Our objective was to evaluate the allelic frequency of natural populations of Ae. aegypti of Mexico at codon 410 of the para gene. Twenty-six Ae. aegypti populations from east and southern Mexico were genotyped for the codon 410 using allele-specific PCR. The frequencies of the L410 allele in Ae. aegypti ranged from 0.10 to 0.99; however, most of the frequencies were in the range of 0.36 to 0.64. The highest frequencies were found in three populations from the state of Veracruz, namely, Minatitlan with 0.99, Poza Rica with 0.82, and Jose Cardel with 0.97, along with populations from Cancun in Quintana Roo with 0.93, Frontera in Tabasco with 0.91, and Ciudad del Carmen in Campeche with 0.86. The frequency of the L410 allele was high in all populations of Ae. aegypti with higher values in populations of the southeast of the country. The knowledge of specific substitutions in vgsc and their interaction to confer resistance is essential to predict and develop future strategies for resistance management in Ae. aegypti in Mexico.

Alterations in life parameters could be due to the accumulation of noxious effects or deleterious genes related to detoxifying enzymes, specifically those coding for mixed-function oxidases, along with the presence of recessive alleles of the V1016I and F1534C mutations, associating deltamethrin resistance with fitness cost in Ae. aegypti. © 2017 Society of Chemical Industry.

This study showed that high frequencies of kdr mutations V1016I and F1534C are reflected in the results of F-RDT and I-RDT tests. Bioassays in conjunction with the characterization of genetic resistance mechanisms are indispensable in the strategic and rational management of resistance in mosquitoes. © 2018 Society of Chemical Industry.

The head louse Pediculus humanus capitis (De Geer) is a hematophagous ectoparasite that inhabits the human scalp. Infestations by this insect are commonly known as pediculosis, which is more common in younger groups. These infestations are asymptomatic; however, skin irritation from scratching occasionally may cause secondary bacterial infections. In recent years, the prevalence of pediculosis has increased in children; this increase has been attributed to louse resistance to the insecticides used as a control measure for infestation. The aim of the present study was to determine the presence and frequency of the knockdown resistance mutation (kdr) T929I in 468 head lice collected from 32 elementary schools in the metropolitan area of Nuevo Leon (24) and Yucatan (8), Mexico. This is the first report of a knockdown resistance (kdr) mechanism in head lice from Mexico. The T929I mutation was present in all of the sampled schools, with variability observed in its allelic and genotypic frequencies.

Culex quinquefasciatus Say is a vector of many pathogens of humans, and both domestic and wild animals. Personal protection, reduction of larval habitats, and chemical control are the best ways to reduce mosquito bites and, therefore, the transmission of mosquito-borne pathogens. Currently, to reduce the risk of transmission, the pyrethroids, and other insecticide groups have been extensively used to control both larvae and adult mosquitoes. In this context, amino acids and acylcarnitines have never been associated with insecticide exposure and or insecticide resistance. It has been suggested that changes in acylcarnitines and amino acids profiles could be a powerful diagnostic tool for metabolic alterations. Monitoring these changes could help to better understand the mechanisms involved in insecticide resistance, complementing the strategies for managing this phenomenon in the integrated resistance management. The purpose of the study was to determine the amino acids and acylcarnitines profiles in larvae of Cx. quinquefasciatus after the exposure to different insecticides. Bioassays were performed on Cx. quinquefasciatus larvae exposed to the diagnostic doses (DD) of the insecticides chlorpyrifos (0.001 μg/mL), temephos (0.002 μg/mL) and permethrin (0.01 μg/mL). In each sample, we analyzed the profile of 12 amino acids and 31 acylcarnitines by LC-MS/MS. A t-test was used to determine statistically significant differences between groups and corrections of q-values. Results indicates three changes, the amino acids arginine (ARG), free carnitine (C0) and acetyl-carnitine (C2) that could be involved in energy production and insecticide detoxification. We confirmed that concentrations of amino acids and acylcarnitines in Cx. quinquefasciatus vary with respect to different insecticides. The information generated contributes to understand the possible mechanisms and metabolic changes occurring during insecticide exposure.

Background: Knockdown resistance (kdr) is the main mechanism that confers resistance to pyrethroids and DDT. This is a product of non-synonymous mutations in the voltage-gated sodium channel (vgsc) gene, and these mutations produce a change of a single amino acid which reduces the affinity of the target site for the insecticide molecule. In Mexico, V410L, V1016I and F1534C mutations are common in pyrethroid-resistant Aedes aegypti (L.) populations. Methods: A multiplex PCR was developed to detect the V410L, V1016I and F1534C mutations in Ae. aegypti. The validation of the technique was carried out by DNA sequencing using field populations previously characterized for the three mutations through allele-specific PCR (AS-PCR) and with different levels of genotypic frequencies. Results: The standardized protocol for multiplex end-point PCR was highly effective in detecting 15 genotypes considering the three mutations V410L, V1106I and F1534C, in 12 field populations of Ae. aegypti from Mexico. A complete concordance with AS-PCR and DNA sequencing was found for the simultaneous detection of the three kdr mutations. Conclusions: Our diagnostic method is highly effective for the simultaneous detection of V410L, V1016I and F1534C, when they co-occur. This technique represents a viable alternative to complement and strengthen current monitoring and resistance management strategies against Ae. aegypti.