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Simple Summary: Diseases transmitted by the mosquito Aedes aegypti, such as dengue, chikungunya and Zika, affect millions of people in tropical and subtropical regions of the world. The sterile insect technique (SIT) is a safe and environmentally benign method of population suppression that could be applied to reduce mosquito-transmitted disease. SIT involves the release of large numbers of sterile male insects that then compete with wild males in mating with females. The females that mate with sterile males do not produce viable offspring. To test this technique within a pilot-scale trial in a village in southern Mexico, we compared two methods for the weekly release of large numbers (approximately 85,000 males/week) of sterile males that were marked with colored powders for later identification. The number of sterile males captured in traps placed in and around houses was higher (average 5.1 males/trap/week) for sterile males released at ground level by technicians walking through the streets of the village. In contrast, traps captured an average of 2.6 males/trap/week when males were released from a small drone aircraft that flew over the village. The males released from the drone may have suffered from chilling, compaction and physical injury during the release procedure. However, the use of the drone resulted in a less aggregated distribution, was markedly quicker, released males over a larger area and required fewer technicians than ground-based releases. Some village residents also reported discomfort from the presence of large numbers of male mosquitoes when released at ground level. Future studies should focus on modifications to the handling and transport of sterile males and the design of drone release containers to avoid injury to sterile mosquitoes and to improve the efficiency of aerial releases for SIT-based suppression of Ae. aegypti in Mexico. Sterile males of Aedes aegypti were released once a week for 8 weeks to evaluate the dispersal efficiency of ground and aerial drone release methods in a rural village of 26 Ha in southern Mexico. Indoor and outdoor BG-Sentinel traps were placed in 13–16 houses distributed throughout the village. The BG traps were activated 48 h after the release of the sterile males and functioned for a 24 h period following each release. Over the 8-week period of simultaneous ground and aerial releases, an average of 85,117 ± 6457 sterile males/week were released at ground level and 86,724 ± 6474 sterile males/week were released using an aerial drone. The ground release method resulted in higher numbers of captured males (mean = 5.1 ± 1.4, range 1.1–15.7 sterile males/trap) compared with the aerial release method (mean = 2.6 ± 0.8, range 0.5–7.3 sterile males/trap) (p < 0.05). Similarly, the prevalence of traps that captured at least one sterile male was significantly higher for ground release compared to the aerial release method (p < 0.01). The lower numbers of sterile males captured in the aerial release method could be due to mortality or physical injury caused by the chilling process for immobilization, or the compaction of these insects during transport and release. However, aerial releases by a two-person team distributed insects over the entire village in just 20 min, compared to ~90 min of work for a five-person team during the ground release method. Ground release also resulted in higher aggregations of males and some villagers reported feeling discomfort from the presence of large numbers of mosquitoes in and around their houses. We conclude that modifications to the handling and transport of sterile males and the design of containers used to store males are required to avoid injury and to improve the efficiency of aerial releases for area-wide SIT-based population suppression programs targeted at mosquito vectors of human disease. [ABSTRACT FROM AUTHOR]

Objective. To compare the efficacy of three modern larvicides with the organophosphate temephos for control of Aedes aegypti in water tanks in Chiapas. Materials and methods. Trials were performed to compare the efficacy of pyriproxyfen, novaluron, two formulations of spinosad (granules and tablets) and temephos in oviposition traps and domestic water tanks. Results. Pyriproxyfen and temephos provided 2-3 weeks of complete control of larvae in oviposition traps, whereas spinosad granules and novaluron provided 7-12 weeks of control. Treatment of water tanks resulted in a significant reduction in oviposition by Ae. aegypti in houses (p<0.001). Higher numbers of larvae were present in temephos and pyriproxyfen-treated water tanks compared to novaluron and spinosad tablet treatments during most of the study. Conclusion. Spinosad formulations and novaluron were effective larvicides in this region. The poor performance of temephos may be indicative of reduced susceptibility in Ae. aegypti populations in Chiapas. [ABSTRACT FROM AUTHOR]

This article explores the regulatory challenges faced when testing genetically modified mosquitoes (GMMs) in Mexico to combat dengue. The researchers stress the need for a comprehensive approach that combines scientific and social considerations in the development of new technologies. The article discusses the regulatory structures and processes involved in obtaining approvals for field trials, including engagement with local communities and adherence to technical regulations. It emphasizes the importance of integrating both technical and community-based regulatory processes to ensure the safety and effectiveness of genetic-based disease control strategies. The article also highlights the involvement of regulatory agencies such as CIBIOGEM and the INSP, as well as the significance of transparent communication and mutual respect in the success of these projects. [Extracted from the article]

Background The larvicidal efficacy of the naturally derived insecticide spinosad, for control of immature stages of Anopheles albimanus and associated culicids, was compared to that of synthetic and biological larvicides. Effects on non-target insects were also determined. Methods A field trial was performed in replicated temporary pools during the rainy season, in southern Mexico. Pools were treated with 10 ppm a.i. spinosad (Tracer 480SC), Bti granules applied at 2 kg/ha (VectoBac WDG, ABG-6511), and 100 ml/ha temephos (50 EC), or an untreated control. Numbers of immature mosquitoes, and aquatic insects in pools were monitored for 20 weeks. Results Samples of immature mosquitoes comprised approximately 10% An. albimanus, 70% Culex spp. (mostly Cx. melanoconion and Cx. coronator) and 20% Uranotaenia lowii. The most effective larvicides were spinosad and temephos that eliminated An. albimanus in 16 out of 20 post-treatment samples, or 9 weeks of continuous control of immature stages, respectively. These larvicides resulted in 15 and 5 weeks of elimination of Culex spp., respectively, or 20 and 4 weeks of continuous elimination of U. lowii, respectively. Bti treatment provided little consistent control. Aquatic insects were recorded comprising 3 orders, 20 families, 40 genera and 44 species. Shannon diversity index values (H') for aquatic insects were highest in the control (0.997) and Bti (0.974) treatments, intermediate in the spinosad treatment (0.638) and lowest in the temephos treatment (0.520). Severely affected non-target insects in the spinosad and temephos treated pools were predatory Coleoptera, Hemiptera and Odonata, which in the case of spinosad was likely due to the high concentration applied. Bti had little effect on aquatic insects. Conclusions The spinosad treatment retained larvicidal activity for markedly longer than expected. Spinosad is likely to be an effective tool for control of anopheline and other pool-breeding mosquitoes in tropical regions. Non-target effects of spinosad on aquatic insects merit further study, but were likely related to the concentration of the product used. [ABSTRACT FROM AUTHOR]

Background The abundance, richness and diversity of mosquitoes and aquatic insects associated with their oviposition sites were surveyed along eight states of the Pacific coast of Mexico. Diversity was estimated using the Shannon index (H'), similarity measures and cluster analysis. Methods Oviposition sites were sampled during 2-3 months per year, over a three year period. Field collected larvae and pupae were reared and identified to species following adult emergence. Aquatic insects present at oviposition sites were also collected, counted and identified to species or genus. Results In total, 15 genera and 74 species of mosquitoes were identified: Anopheles pseudopunctipennis, An. albimanus and Aedes aegypti were the most abundant and widely distributed species, representing 47% of total mosquito individuals sampled. New species records for certain states are reported. Anopheline diversity was lowest in Sinaloa state (H' = 0.54) and highest in Chiapas (H' = 1.61) and Michoacán (H' = 1.56), whereas culicid diversity was lowest in Michoacán (H' = 1.93), Colima (H' = 1.95), Sinaloa (H' = 1.99) and Jalisco (H' = 2.01) and highest in Chiapas (H' = 2.66). In total, 10 orders, 57 families, 166 genera and 248 species of aquatic insects were identified in samples. Aquatic insect diversity was highest in Chiapas, Oaxaca and Michoacán (H' = 3.60-3.75). Mosquito larval/pupal abundance was not correlated with that of predatory Coleoptera and Hemiptera. Conclusion This represents the first update on the diversity and geographic distribution of the mosquitoes and aquatic insects of Mexico in over five decades. This information has been cataloged in Mexico's National Biodiversity Information System (SNIB-CONABIO) for public inspection. [ABSTRACT FROM AUTHOR]

BACKGROUND: Field trials were conducted during the wet and dry seasons in periurban and semi-rural cemeteries in southern Mexico to determine the efficacy of a suspension concentrate formulation of spinosad (Tracer 480SC) on the inhibition of development of Aedes albopictus L. and Ae. aegypti Skuse. For this, oviposition traps were treated with spinosad (1 or 5 mg L [ABSTRACT FROM AUTHOR]

Background: Aedes aegypti, the ‘yellow fever mosquito’, is the primary vector to humans of dengue and yellow fever flaviviruses (DENV, YFV), and is a known vector of the chikungunya alphavirus (CV). Because vaccines are not yet available for DENV or CV or are inadequately distributed in developing countries (YFV), management of Ae. aegypti remains the primary option to prevent and control outbreaks of the diseases caused by these arboviruses. Permethrin is one of the most widely used active ingredients in insecticides for suppression of adult Ae. aegypti. In 2007, we documented a replacement mutation in codon 1,016 of the voltage-gated sodium channel gene (para) of Ae. aegypti that encodes an isoleucine rather than a valine and confers resistance to permethrin. Ile1,016 segregates as a recessive allele conferring knockdown resistance to homozygous mosquitoes at 5–10 mg of permethrin in bottle bioassays. Methods and Findings: A total of 81 field collections containing 3,951 Ae. aegypti were made throughout Me´xico from 1996 to 2009. These mosquitoes were analyzed for the frequency of the Ile1,016 mutation using a melting-curve PCR assay. Dramatic increases in frequencies of Ile1,016 were recorded from the late 1990’s to 2006–2009 in several states including Nuevo Leo´n in the north, Veracruz on the central Atlantic coast, and Yucata´n, Quintana Roo and Chiapas in the south. From 1996 to 2000, the overall frequency of Ile1,016 was 0.04% (95% confidence interval (CI95) = 0.12%; n = 1,359 mosquitoes examined). The earliest detection of Ile1,016 was in Nuevo Laredo on the U.S. border in 1997. By 2003–2004 the overall frequency of Ile1,016 had increased ,100-fold to 2.7% (60.80% CI95; n = 808). When checked again in 2006, the frequency had increased slightly to 3.9% (61.15% CI95; n= 473). This was followed in 2007–2009 by a sudden jump in Ile1,016 frequency to 33.2% (61.99% CI95; n = 1,074 mosquitoes). There was spatial heterogeneity in Ile1,016 frequencies among 2007–2008 collections, which ranged from 45.7% (62.00% CI95) in the state of Veracruz to 51.2% (64.36% CI95) in the Yucata´n peninsula and 14.5% (62.23% CI95) in and around Tapachula in the state of Chiapas. Spatialheterogeneity was also evident at smaller geographic scales. For example within the city of Chetumal, Quintana Roo, Ile1,016 frequencies varied from 38.3%–88.3%. A linear regression analysis based on seven collections from 2007 revealed that the frequency of Ile1,016 homozygotes accurately predicted knockdown rate for mosquitoes exposed to permethrin in a bioassay (R2 = 0.98). Conclusions: We have recorded a dramatic increase in the frequency of the Ile1,016 mutation in the voltage-gated sodium channel gene of Ae. aegypti in Me´xico from 1996 to 2009. This may be related to heavy use of permethrin-based insecticides in mosquito control programs. Spatial heterogeneity in Ile1,016 frequencies in2007 and 2008 collections may reflect differences in selection pressure or in the initial frequency of Ile1,016. The rapid recent increase in Ile1,016 is predicted by a simple model of positive directional selection on a recessive allele. Unfortunately this model also predicts rapid fixation of Ile1,016 unless there is negative fitness associated with Ile1,016 in the absence of permethrin. If so, then spatial refugia of susceptible Ae. aegypti or rotational schedules of different classes of adulticides could be established to slow or prevent fixation of Ile 1,016. [ABSTRACT FROM AUTHOR]

Simple Summary: Diseases transmitted by Aedes mosquitoes, such as dengue, Zika, and chikungunya, are a public health problem of growing global concern. There are several strategies for mosquito control. One of them is the Sterile Insect Technique, which is a method of breeding millions of mosquitoes, where radiation is used in males to sterilize them. Then, the males are released into the wild. These sterile males mate with wild females without having offspring, thus decreasing field populations. However, one of the problems is being able to have a large number of viable eggs for these field operations. Therefore, this study evaluates the temporal viability of Aedes mosquito eggs employing two substances, such as hydrolyzed collagen and Hyalurosmooth®. These two moisturizing substances maintained viable Aedes. aegypti eggs for up to eight weeks. Dengue and other Aedes-borne diseases have dramatically increased over the last decades. The Sterile Insect Technique (SIT) has been successfully used as part of integrated pest strategies to control populations of insect-plant and livestock pests and is currently being tested as a potential method to reduce mosquito populations in an environmentally friendly approach. However, during the mass rearing steps needed to produce millions of mosquitoes, egg storage and preservation are essential for a certain amount of time. Eggs of Aedes aegypti have a chorionic pad that functions as a sticky substance to glue them onto the inner walls of larval breeding sites. The chorionic pad is chemically made of hyaluronic acid, a hygroscopic compound, responsible to protect them from desiccation over time. Two commercial products with hygroscopic properties, hydrolyzed collagen, and Hyalurosmooth®, both were tested to assess their ability to prolong egg life storage for A. aegypti and A. albopictus. Results showed that 85–95% of Ae. aegypti eggs were able to hatch up to week 8 after being treated with both hydrophilic compounds, compared with the control 66.3%. These two substances showed promising effects for keeping Ae. aegypti eggs viable during prolonged storage in mass rearing insect production focused on vector control SIT programs. [ABSTRACT FROM AUTHOR]

Odonate nymphs are important predators of the immature aquatic stages of mosquitoes. Populations of the malaria vector Anopheles pseudopunctipennis Theobald (Diptera: Culicidae) can be efficiently reduced by extraction of filamentous algae from river pools in southern Mexico. Here, we examined the influence of this intervention on the diversity of odonates associated with mosquito breeding pools after annual extractions of algae from river pools in a 3-km section of the Coatán River, over a period of 2 yr. Odonate sampling was performed at monthly intervals in control and treated sections of the river for 4-5 mo after extraction in both years and before extraction in 1 yr. In total, 16 species, 10 genera, and 6 families of odonates were collected. Shannon diversity index values declined significantly during a period of 1 mo in 2001 and >5 mo in 2002. However, the abundance of odonates captured was not affected by algal extraction. In contrast, year-to-year variation in the diversity and abundance of the odonate community was strongly influenced by precipitation and river volume. Despite the importance of algae in river ecology, we conclude that the mosquito control intervention resulted in minimal impact on the odonate community in southern Mexico. [ABSTRACT FROM AUTHOR]

Simple Summary: The sterile insect technique (SIT) involves the release of massive numbers of male insects that have been sterilized by irradiation treatment during their development. Wild females that mate with sterilized males are not able to produce offspring, resulting in rapid decline in the target insect population over a large area. The success of this technique depends on the ratio of wild:sterile males achieved following male releases and the ability of sterile males to mate with wild females, i.e., their sexual competitiveness compared to fertile wild male insects. There is growing interest in applying SIT to the area-wide control of mosquitoes, such as Aedes aegypti and Aedes albopictus, that transmit important human diseases caused by dengue, chikungunya, and Zika viruses. In the present study, the sexual competitiveness of both mosquito species was affected by irradiation treatments but did not vary greatly with different ratios of fertile:sterile males in mating cages. Most importantly, the fertility of eggs was greatly reduced when more sterile males were present in mating cages, resulting in an 88% decrease in the production of fertile eggs by both species of mosquitoes in some experiments. We will use these results to perform small-scale trials in rural villages frequently affected by outbreaks of mosquito-borne diseases in southern Mexico. The sterile insect technique may prove useful for the suppression of mosquito vectors of medical importance in regions where arboviruses pose a serious public health threat. In the present study, we examined the effects of sterilizing irradiation doses across different ratios of fertile:irradiated males on the mating competitiveness of Ae. aegypti and Ae. albopictus under laboratory and field-cage conditions. For both species, the percentage of females inseminated and the number of eggs laid over two gonotrophic cycles varied significantly in mating treatments involving 1:1, 1:5, and 1:10 fertile:irradiated males compared to controls of entirely fertile or entirely irradiated males but was not generally affected by the irradiation dose. Egg hatching was negatively affected in females exposed to increasing proportions of irradiated males in both laboratory and field cages. Male competitiveness (Fried's index) values varied from 0.19 to 0.58 in the laboratory and were between 0.09 and 1.0 in field cages, depending on th species. Competitiveness values were negatively affected by th eirradiation dose in both species under field-cage conditions, whereas in the laboratory, Ae. albopictus was sensitive to the dose but Ae. aegypti was not. In general, male competitiveness was similar across all mating regimes. Most importantly, induced egg sterility was positively correlated with the proportion of irradiated males present in the mating treatments, reaching a maximum of 88% under field-cage conditions for both Ae. aegypti and Ae. albopictus males treated with 50 and 40 Gy irradiation, respectively. These results indicate that sterile males produced at our facility are suitable and competitive enough for field pilot SIT projects and provide guidance to decide the optimal sterile:fertile ratios. [ABSTRACT FROM AUTHOR]

Simple Summary: Aedes aegypti and Ae. albopictus are the most important mosquito vectors of dengue, chikungunya and Zika virus. There is growing interest in the control of these vectors using the sterile insect technique in which large numbers of sterilized males are released and compete with wild fertile males for mates. Females that mate with sterile males do not produce viable offspring. A study was performed on the population fluctuations of Ae. aegypti and Ae. albopictus using egg traps in two rural villages with a history of dengue in Chiapas, southern Mexico. Higher numbers of Aedes eggs were recorded in Hidalgo village compared with the village of Río Florido. In contrast, higher number of eggs were collected in areas surrounding Río Florido, compared with those around Hidalgo. Aedes aegypti was the dominant species during the dry season and at the start of the rainy season in both villages. Aedes albopictus populations were lower for most of the dry season, but increased during the rainy season and became dominant at the end of the rainy season in both villages. Aedes albopictus was also the dominant species in the zones of natural vegetation surrounding both villages. We conclude that the efficacy of a program of vector control involving the sterile insect technique could be evaluated in future studies on the isolated mosquito populations in these rural villages, in combination with habitat elimination and appropriate treatment of water sources. Indoor and outdoor ovitraps were placed in 15 randomly selected houses in two rural villages in Chiapas, southern Mexico. In addition, ovitraps were placed in five transects surrounding each village, with three traps per transect, one at the edge, one at 50 m, and another at 100 m from the edge of the village. All traps were inspected weekly. A transect with eight traps along a road between the two villages was also included. Population fluctuations of Aedes aegypti and Ae. albopictus were examined during 2016–2018 by counting egg numbers. A higher number of Aedes spp. eggs was recorded at Hidalgo village with 257,712 eggs (60.9%), of which 58.1% were present in outdoor ovitraps and 41.9% in indoor ovitraps, compared with 165,623 eggs (39.1%) collected in the village of Río Florido, 49.0% in outdoor and 51.0% in indoor ovitraps. A total of 84,047 eggs was collected from ovitraps placed along transects around Río Florido, compared to 67,542 eggs recorded from transects around Hidalgo. Fluctuations in egg counts were associated with annual variation in precipitation, with 2.3 to 3.2-fold more eggs collected from ovitraps placed in houses and 4.8 to 5.1-fold more eggs in ovitraps from the surrounding transects during the rainy season than in the dry season, respectively. Aedes aegypti was the dominant species during the dry season and at the start of the rainy season in both villages. Aedes albopictus populations were lower for most of the dry season, but increased during the rainy season and predominated at the end of the rainy season in both villages. Aedes albopictus was also the dominant species in the zones surrounding both villages. The numbers of eggs collected from intradomiciliary ovitraps were strongly correlated with the numbers of eggs in peridomiciliary ovitraps in both Río Florido (R2adj = 0.92) and Hidalgo (R2adj = 0.94), suggesting that peridomiciliary sampling could provide an accurate estimate of intradomiciliary oviposition by Aedes spp. in future studies in these villages. We conclude that the feasibility of sterile insect technique (SIT)-based program of vector control could be evaluated in the isolated Ae. aegypti populations in the rural villages of our baseline study. [ABSTRACT FROM AUTHOR]

• The study shows a high acceptance of the SIT in both communities. • Women were more responsive to surveys than men. • Risk factors: being from the community Hidalgo and believing that sterile mosquitoes bite. Protective factors: favourable opinion about the SIT-project workers and the possible management of the SIT-project by the SSA. • Interdisciplinary and intersectoral collaborations are essential for SIT acceptance. Worldwide, vector-transmitted diseases account for more than 17% of all infectious diseases and cause more than 700,000 deaths annually. The primary strategy to control the transmission of dengue, chikungunya and Zika focuses on the control of their vectors. Vector control programs depend mainly on the use of insecticides. However, these measures have failed to yield the desired results because the lack of proper control decreases their effectiveness over time. Also, the effect of insecticide use on non-target organisms, environmental contamination, and the development of insecticide resistance impose continuous challenges for insecticide-dependant control programs. The sterile insect technique, on the other hand, is a non-polluting and environment-friendly technique. The use of sterile insects is generally well established in agriculture, but human health interventions often require a consensus that combines social perceptions with scientific evidence. Factors associated with acceptance of the releases of sterile male Aedes aegypti mosquitoes were assessed with logistic regression models for two communities (Rio Florido and Hidalgo) in Tapachula, Chiapas, Mexico. The favourable opinion of the respondents about the project workers, and the fact that the releases of sterile mosquitoes would be managed by the Secretaría de Salud , were found to be factors that supported the acceptance of sterile mosquito releases. Factors associated with disapproval were community (Rio Florido and Hidalgo) and the misbelief that sterile male mosquitoes can bite. The differences observed between the communities included in this study might be the result of experiences with the releases, of social and community organisation, and of leadership by social actors. [Display omitted] [ABSTRACT FROM AUTHOR]