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Objective. To evaluate indoor use of commercial aerosols for dengue vector mosquito control, and estimate the number of treatable houses per can. Materials and methods. Four aerosol products containing combinations of pyrethroids (two containing propoxur and one containing synergists too), were evaluated with mosquitoes in a room of a Tapachulastyle house. Eight cages containing 20 insecticide susceptible or resistant females were hung from tripods, another set was placed in sheltered areas of the room. From the entrance of the room, one of 4-9 concentrations was sprayed for each aerosol, leaving the mosquitoes for 30 min after sprayed. Mortality was recorded after 24 h and lethal concentrations were calculated. Results. Aerosol A had the highest LC50, with 0.308 g for mosquitoes hanging from tripods and 0.453 g for sheltered mosquitoes; followed by aerosols C, D and B, with statistical differences between types of exposure. Conclusions. Aerosols B-D could spray 20-25 3-room houses (56 m3-room), killing all resistant mosquitoes. Aerosols may become a good tool for indoor mosquito control, if the optimal concentration and correct spray method are used.

Pyrethroid resistance inAedes aegyptihas become widespread after almost two decades of frequent applications to reduce the transmission of mosquito-borne diseases. Because few insecticide classes are available for public health use, insecticide resistance management (IRM) is proposed as a strategy to retain their use. A key hypothesis of IRM assumes that negative fitness is associated with resistance, and when insecticides are removed from use, susceptibility is restored. In Tapachula, Mexico, pyrethroids (PYRs) were used exclusively by dengue control programs for 15 years, thereby contributing to selection for high PYR resistance in mosquitoes and failure in dengue control. In 2013, PYRs were replaced by organophosphates—insecticides from a class with a different mode of action. To test the hypothesis that PYR resistance is reversed in the absence of PYRs, we monitoredAe. aegypti’sPYR resistance from 2016 to 2021 in Tapachula. We observed significant declining rates in the lethal concentration 50 (LC50), for permethrin and deltamethrin. For each month following the discontinuation of PYR use by vector control programs, we observed increases in the odds of mosquitoes dying by 1.5% and 8.4% for permethrin and deltamethrin, respectively. Also, knockdown-resistance mutations (kdr) in the voltage-gated sodium channel explained the variation in the permethrin LC50s, whereas variation in the deltamethrin LC50s was only explained by time. This trend was rapidly offset by application of a mixture of neonicotinoid and PYRs by vector control programs. Our results suggest that IRM strategies can be used to reverse PYR resistance inAe. aegypti; however, long-term commitment by operational and community programs will be required for success.Author summaryThe mosquitoAedes aegyptiis the principal urban vector of the viruses that cause three globally significant diseases: dengue fever, chikungunya, and Zika fever, for which vaccines and effective treatments are currently absent. The only way to control dengue, chikungunya, and Zika fever outbreaks is to diminish vector populations. During epidemics, the most frequent way of targeting adult mosquitoes is outdoor spatial spraying of insecticides. Control ofAe. aegyptiis difficult because limited insecticide classes are available for public health, leading to operational practices that overuse single molecules for long periods of time, imposing great selection pressure on mosquito populations for insecticide resistance. Insecticide resistance management (IRM) is proposed as a strategy to prevent resistance and avoid depleting the susceptibility resource in mosquito populations. IRM strategies assume that alternation of insecticides with different toxicological modes of action will prevent the selection of resistance. Unfortunately, very few field evaluations have reported IRM schemes to controlAe. aegypti. In our study, the exclusive use of pyrethroids in vector control programs in Mexico from 1999 to 2013, led in the selection of knockdown resistance (kdr) to pyrethroid insecticides. To address this issue, vector control programs temporarily phased out pyrethroids from 2013 to 2019, substituting them with an insecticide class with a different mode of action: organophosphates (OPs). During six years, we monitored pyrethroid resistance in 24 mosquito populations from Tapachula, Mexico. We show that discontinuing pyrethroids for six years led in pyrethroid resistance reversal inAe. aegyptiin the field. However, high levels of pyrethroid resistance continue to jeopardize operational application, necessitating longer periods of pyrethroid cessation and novel IRM strategies to achieve lower resistance thresholds.

La gran cantidad de residuos plásticos los hace una fuente de materia prima a través del reciclaje. El polietileno de alta densidad es el segundo plástico más consumido y producido en México y a nivel global. En la presente investigación se ha generado el diseño de un material compuesto, con matriz de polietileno de alta densidad reciclado, reforzado por fibra de vidrio corta clase E, con el objetivo de producir perfiles estructurales que se utilicen en armaduras para cubiertas ligeras de gran claro. Se ha realizado la caracterización mecánica del material, para conocer las propiedades a tensión y a compresión. También la caracterización física para conocer la densidad y expansión térmica lineal. Así como la caracterización térmica, con el objetivo de conocer los parámetros de producción y estabilidad térmica. Los resultados obtenidos de la caracterización mecánica y física, se introducirán en una herramienta digitad para conocer la utilidad del material conforme al análisis y diseño estructural, aplicado a la arquitectura.

There are major public health concerns regarding the spread of mosquito-borne diseases such as dengue, Zika, and chikungunya, which are mainly controlled by using insecticides against the vectors, Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse). Pyrethroids are the primary class of insecticides used for vector control, due to their rapid knockdown effect and low toxicity to vertebrates. Unfortunately, continued use of pyrethroids has led to widespread insecticide resistance in Ae. aegypti; however, we lack information for Ae. albopictus—a sympatric species in Chiapas since 2002. In this study, we evaluated the permethrin resistance status of Ae. albopictus collected from Mexico and Texas. We also selected for permethrin resistance in the laboratory and investigated the potential mechanisms conferring resistance in this species. Knockdown resistance mutations, specifically F1534C, in the voltage-gated sodium channel gene, and increased activity of detoxifying enzymes were evaluated. Low levels of permethrin resistance (58-fold) found in Ae. aegypti from the same sites in Mexico. This research indicates the importance of continued monitoring of Ae. albopictus populations to prevent resistance from developing in the future.

The feasibility of the use of WHO impregnated paper and biochemical assays to determine lethal concentrations (LC50 and LC99) and insecticide metabolic enzyme levels of Triatoma dimidiata.LC50 and LC99 were calculated with WHO papers impregnated at different concentrations of malathion, propoxur and deltamethrin; the percentage of insensitive acetylcholinesterase (iAChE); and the levels of esterases, glutathione S-transferases, and monooxygenases in laboratory nymphs of the first stage (5 to 7 days), were undertaken using the WHO biochemical assays.Respectively the LC50 and LC99 μg/cm2 obtained for malathion were 43.83 and 114.38, propoxur 4.71 and 19.29, and deltamethrin 5.80 and 40.46. A 30% of the population had an iAChE, and only a few individuals had high P450 and β-eterase levels.Impregnated papers and biochemical tests developed by WHO for other insects, proved to be feasible methods in monitoring insecticide resistance and metabolic enzymes involved in T. dimidiata.La factibilidad de usar los papeles impregnados y ensayos bioquímicos según la OMS para determinar concentraciones letales (CL50 y CL99) y niveles enzimáticos en la resistencia a insecticidas en Triatoma dimidiata.Se calcularon la CL50 y CL99 con papeles impregnados según la OMS a diferentes concentraciones de malatión, propoxur y deltametrina; el porcentaje de acetilcolinesterasa insensible (iAChE); y los niveles de esterasas, glutatión S-transferasas, y monooxigenasas en ninfas de laboratorio del estadio I (5-7 días) se determinaron usando los ensayos bioquímicos según la OMS.Se obtuvieron las CL50 y CL99 μg / cm2 respectivamente para malatión 43.83 y 114.38, propoxur 4.71 y 19.29, y deltametrina 5.80 y 40.46. Un 30% de las chinches tuvo iAChE, y sólo pocos individuos tuvieron niveles superiores de P450 y β-eterasas.Los papeles impregnados y ensayos bioquímicos que describe la OMS para otros insectos demostraron ser métodos factibles para monitorear la resistencia a insecticidas y las enzimas metabólicas involucradas en T. dimidiata.

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., Author summary Dengue, Zika, and chikungunya are viral diseases transmitted by the mosquito Aedes aegypti. Unfortunately, no vaccines or effective treatments are available, and public health strategies rely on the suppression of mosquito populations to reduce the impact of disease outbreaks. Pyrethroids are a common class of insecticides used to suppress mosquito populations. Unfortunately, mosquitoes have developed resistance to pyrethroids in several regions of the world, threatening disease control efforts. Since few classes of insecticides are available for public health, we have to find strategies that prevent or prolong the use of pyrethroids. Therefore, we need to understand mechanisms of resistance and develop methods to quantify these mechanisms in field populations before they become a threat to vector control strategies. Quantifying the frequency of mutations associated with target site resistance provides information about the presence of this mechanism in mosquito populations; however, we still need to understand additional mechanisms of resistance (e.g., metabolism, cuticle penetration) that play an important role in the survival of mosquitoes. In this study, we sequenced the genome of resistant (kdr), recovered, and dead mosquitoes after insecticide exposure. Our aim is to identify genomic variants associated with specific mechanisms of resistance. The results will improve the identification of specific genomic markers associated with resistance in the Aedes aegypti from Southeastern Mexico.

Background Insecticide use continues as the main strategy to control Aedes aegypti, the vector of dengue, Zika, chikungunya, and yellow fever. In the city of Tapachula, Mexico, mosquito control programs switched from pyrethroids to organophosphates for outdoor spatial spraying in 2013. Additionally, the spraying scheme switched from total coverage to focused control, prioritizing areas with higher entomological-virological risk. Five years after this strategy had been implemented, we evaluated the status and variability of insecticide resistance among Ae. aegypti collected at 26 sites in Tapachula. Methodology/Principal findings We determined the lethal concentrations at 50% of the tested populations (LC50) using a bottle bioassay, and then, we calculated the resistance ratio (RR) relative to the susceptible New Orleans strain. Permethrin and deltamethrin (pyrethroids), chlorpyrifos and malathion (organophosphates), and bendiocarb (carbamate) were tested. The frequencies of the substitutions V1016I and F1534C, which are in the voltage-gated sodium channel and confer knockdown-resistance (kdr) to pyrethroid insecticides, were calculated. Despite 5 years having passed since the removal of pyrethroids from the control programs, Ae. aegypti remained highly resistant to permethrin and deltamethrin (RR > 10-fold). In addition, following 5 years of chlorpyrifos use, mosquitoes at 15 of 26 sites showed moderate resistance to chlorpyrifos (5- to 10-fold), and the mosquitoes from one site were highly resistant. All sites had low resistance to malathion (< 5-fold). Resistance to bendiocarb was low at 19 sites, moderate at five, and high at two. Frequencies of the V1016I ranged from 0.16–0.71, while C1534 approached fixation at 23 sites (0.8–1). Resistance profiles and kdr allele frequencies varied across Tapachula. The variability was not associated with a spatial pattern at the scale of the sampling. Conclusion/Significance Mosquito populations respond to selection pressure at a focal scale in the field. Spatial variation across sites highlights the importance of testing multiple sites within geographical regions., Author summary Aedes aegypti is a major vector of dengue, chikungunya, Zika, and yellow fever. In the absence of effective vaccines or treatments, the suppression of mosquito populations using insecticides commonly has been implemented by public health programs. Unfortunately, few insecticides are available to target adult mosquitoes with outdoor spraying. The mismanagement of insecticides can lead to resistance selection in mosquitoes, affecting our ability to control arboviral diseases. Ideally, screening insecticide susceptibility in local mosquito populations allows public health entities to support insecticide management strategies that will prevent the development of resistance. In this study, we evaluated insecticide resistance in Ae. aegypti collected across 26 sites in Tapachula, Mexico. The results reveal the response of populations to its historic use of insecticides. High resistance to pyrethroids, used for 10 years, but not in the previous 5 years, and moderate to high resistance to chlorpyrifos, an insecticide from a different toxicological group and used for the past 5 years, were confirmed. High variation in resistance across Ae. aegypti sites suggests that focal selection plays an important role in the evolution of insecticide resistance in the field. Screening several collections sites within a geographical region provides better evidence to support strategies of insecticide management.

The El Tatio Geyser Field (ETGF), located in Northern Chile, is the main geyser field in the southern hemisphere. Despite this, details of its microbial ecology are still unknown. Here, we briefly report on the composition and predicted functions of the bacterial community in spouting pool sediments from the ETGF as revealed by high-throughput sequencing of 16S rRNA genes. Results of this analysis showed that while there were differences in richness and diversity between samples, bacterial communities were primarily dominated by the phyla Proteobacteria, followed Firmicutes, Bacteroidetes, Acidobacteria, and Chloroflexi. Analyses of predicted functional activity indicated that the functions were mostly attributed to chemoheterotrophy and aerobic chemoheterotrophy, followed by sulfur (respiration of sulfur compounds and sulfate) and nitrogen (nitrate reduction, respiration of nitrogen and nitrate) cycling. Taken together, our results suggest a high diversity in taxonomy and predictive functions of bacterial communities in sediments from spouting pools. This study provides fundamentally important information on the structure and function predictive functions of microbiota communities in spouting pools. Moreover, since the ETGF is intensively visited and impacted by tens of thousands of tourists every year, our results can be used to help guide the design of sustainable conservation strategies.

This chapter examines the role of formal and nonformal leaders in creating culturally proficient educational practices to create equity and access for all students. Transformative leadership is the foundation of this change process. Through the inside-out cultural proficiency journey, all educational stakeholders can create equity and access at the intersection of race, measurement, and conversations. This chapter introduces a study-in-progress with the following research question: What does it take for educational leaders to create and sustain change processes focused on culturally proficient educational practices so that all students achieve?

Dengue is one of the most important vector-borne diseases worldwide and is a public health problem in Mexico. Most programs in dengue endemic countries rely on insecticides for Aedes control. In Mexico, pyrethroid insecticides (mainly permethrin and deltamethrin) have been extensively used over a decade as adulticides and represented a strong selection for insecticide resistance for dengue vectors in several parts of the country. We studied the type, frequency and distribution of insecticide resistance mechanisms in Aedes aegypti from six municipalities in the state of Guerrero selected on the basis of historically intense chemical control and a high risk for dengue transmission. Ae. aegypti eggs were collected from October 2009 to January 2010 using ovitraps. F1 adults, emerged from these collections, were exposed to permethrin, deltamethrin and DDT in WHO diagnostic tests and showed high resistance levels to both pyrethroids and DDT. This was consistent with the presence of increased metabolic enzyme activities and target site insensitivity due to kdr mutations. Biochemical assays showed elevated esterase and glutathione S-transferase activities in the six municipalities. The V1016I kdr mutation on the IIS6 domain of the sodium channel gene was present in an overall frequency of 0.80. A second mutation, F1534C on the IIIS6 domain of the same gene was also detected, being the first report of this mutation in Guerrero. The multiple resistance mechanisms present in Ae. aegypti from Guerrero state represent a warning for the efficacy of the pyrethroid usage and consequently for the success of the dengue control program.

Resumen en español: "Las enfermedades transmitidas por vectores representan un importante problema de salud pública. Una de las más importantes es el dengue, transmitido por el mosquito Aedes aegypti, que además ha sido responsable de la transmisión de enfermedades de reciente ingreso en México como la chikungunya (CHIK) en 2015 (Díaz-González et al., 2015) y del zika, en un evento posterior al CHIK (Boletín epidemiológico 2016). Desde 1960 y hasta el presente, los programas de control de vectores en México han usado diferentes insecticidas para el control químico de Ae. aegypti (NOM-032-SSA2-2002, NOM-0032-SSA-2014), al igual que lo han hecho diferentes programas de control de vectores en el mundo, haciendo uso de insecticidas de diferentes grupos toxicológicos como órganoclorados (OCl), organofosforados (OP), carbamatos (CARB) y piretroides (PYRs) (Karunamoorthi y Sabesan, 2013). El uso prolongado y desmedido de insecticidas como control químico, sin una estrategia real para su manejo, ha generado resistencia en los vectores, lo que ha ocasionado un impacto importante sobre los diferentes programas de salud, obligando a cambiar las estrategias de control (WHO 1996). "

Biochemical assays on Anopheles albimanus collected for 3 years in southern Mexico villages after house spraying of a single insecticide [DDT or a pyrethroid (PYR)], a two insecticide mosaic [organophosphate (OP)/PYR] or a three insecticide annual rotation (OP-PYR-carbamate), defined the relative rates of selection of glutathione S-transferase-based resistance. After 3 years of rotation, mosaic and single PYR strategies, there was a decrease in the glutathione S-transferase (GST) activity, returning to susceptible levels, with few variations. In the rotation strategy, GST activity increased significantly in one group of villages, when OP treatment was replaced by the PYR in the 2nd treatment year. While, GST activity increased only in one village out of six continuously PYR-treated in the 1st year. In the DDT-treated villages, one group had increased activity in the 1st year, but this declined in years 2 and 3; GST activity of the other DDT-treated group were unchanged during the trial.

Payment systems play a key role in the financial infrastructure of all modern economies. Participants of payment systems need access to intraday liquidity to fulfill their payment obligations. They do that either using their own funds, which are costly, or recycling incoming payment. In order to rely on incoming payments, banks could delay the settlement of their own payment obligations. From the regulators’ point of view it is important to know to what degree participants rely on the payments they receive from others. In Mexico, this is among the first studies that analyze from this perspective the intraday liquidity management of the Real Time Settlement Payment System, SPEI. We examine a data set of transactions from April 7 to May 7, 2010 in order to get insights of the participants’ behavior regarding the delay of sending payment orders.

Blood flow dynamics under physiologically realistic pulsatile conditions plays an important role in the growth, rupture and surgical treatment of intracranial aneurysms. This paper describes the flow dynamics and arterial wall interaction in a representative model of a terminal aneurysm of the basilar artery, and compares its wall shear stress, pressure, effective stress and wall deformation with those of a healthy basilar artery. The arterial wall was assumed to be elastic or hyperelastic, isotropic, incompressible and homogeneous. The flow was assumed to be laminar, Newtonian, and incompressible. The fully coupled fluid and structure models were solved with the finite elements package ADINA. The intra-aneurysmal pulsatile flow shows single recirculation region during both systole and diastole. The pressure and shear stress on the aneurysm wall exhibit large temporal and spatial variations. The wall thickness, the Young’s modulus in the elastic wall model and the hyperelastic Mooney–Rivlin wall model affect the aneurysm deformation and effective stress in the wall especially at systole.

This article reviews Soft Matter Physics. by Masao Doi 268 pp. , Oxford, UK. 2013. Price $74.95 (hardcover) ISBN 978-0-19-965295-2.