Seroprevalence of Trypanosoma cruzi among children from Veracruz, Mexico: Epidemiological baseline for a control model based on Chagas disease active transmission / Seroprevalencia de Trypanosoma cruzi en niños de Veracruz, México: línea epidemiológica de base para un modelo de control fundamentado de la transmisión activa de la enfermedad de Chagas.

Introduction. In 2021, the Secretaría de Salud de México and the Pan American Health Organization launched an initiative to interrupt intra-domiciliary vector transmission of Trypanosoma cruzi based on the prevalence of Chagas disease in children. The Mexican State of Veracruz was leading this initiative. Objective. To estimate the seroprevalence of T. cruzi infection among children under 15 years of age from rural areas of Veracruz, México. Materials and methods. We identified eight localities of high priority from the Municipality of Tempoal, Veracruz, for baseline serology. Blood samples were collected on filter paper from 817 individuals between June and August 2017, for screening with a third-generation enzyme immunoassay. Reactive cases were confirmed by indirect hemagglutination, enzyme-linked immunosorbent assay, and indirect immunofluorescence tests on peripheral blood serum samples. We calculated seroprevalence and 95% confidence intervals (CI). Results. We confirmed Chagas disease cases in children under 15 years of age with a seroprevalence of 1,9% (95 % CI = 1,12-3,16) in the localities of Citlaltepetl, Cornizuelo, Cruz de Palma and Rancho Nuevo. Conclusions. These results indicate recent transmission of T. cruzi in these communities and allow to establish an epidemiological baseline for the design and implementation of a model focused on geographical areas with active transmission to advance toward the elimination of intra-domiciliary vector transmission of this parasite in Mexico.

Introducción. En el 2021, la Secretaría de Salud de México y la Organización Panamericana de la Salud lanzaron una iniciativa para interrumpir la transmisión vectorial intradomiciliaria de Trypanosoma cruzi, fundamentada en la prevalencia de la enfermedad de Chagas en la población infantil. El estado mexicano de Veracruz fue el pionero de esta iniciativa. Objetivo. Estimar la seroprevalencia de infección por T. cruzi en menores de 15 años de localidades rurales de Veracruz, México. Materiales y métodos. Se identificaron ocho localidades prioritarias para la serología basal del municipio de Tempoal, Veracruz. Entre junio y agosto de 2017, se recolectaron muestras de sangre en papel filtro de 817 individuos para su tamizaje mediante un inmunoensayo enzimático de tercera generación. Los casos reactivos del tamizaje se confirmaron mediante pruebas de hemaglutinación indirecta, ensayo de inmunoabsorción ligado a enzimas e inmunofluorescencia indirecta en muestras de suero. Se calculó la seroprevalencia y su intervalo de confianza (IC) del 95 %. Resultados. En las localidades de Citlaltépetl, Cornizuelo, Cruz de Palma y Rancho Nuevo se confirmaron casos de la enfermedad de Chagas en menores de 15 años con una seroprevalencia de 1,9 % (IC 95 % = 1,12-3,16). Conclusiones. Los resultados indican que estas comunidades presentan transmisión reciente de T. cruzi y permiten establecer una línea epidemiológica de base para el diseño e implementación de un modelo dirigido a aquellas áreas geográficas con transmisión activa. Se espera que dicho modelo contribuya a la eliminación de la transmisión vectorial intradomiciliaria del tripanosomátido en México.

Evidence of Ongoing Transmission of Zika Virus in Mérida, Mexico.

Since the Zika virus (ZIKV) pandemic in 2015-2017, there has been a near absence of reported cases in the Americas outside of Brazil. However, the conditions for Aedes-borne transmission persist in Latin America, and the threat of ZIKV transmission is increasing as population immunity wanes. Mexico has reported only 70 cases of laboratory-confirmed ZIKV infection since 2020, with no cases recorded in the Yucatán peninsula. Here, we provide evidence of active ZIKV transmission, despite the absence of official case reports, in the city of Mérida, Mexico, the capital of the state of Yucatán. Capitalizing on an existing cohort, we detected cases in participants with symptoms consistent with flavivirus infection from 2021 to 2022. Serum samples from suspected cases were tested for ZIKV RNA by polymerase chain reaction or ZIKV-reactive IgM by ELISA. To provide more specific evidence of exposure, focus reduction neutralization tests were performed on ELISA-positive samples. Overall, we observed 25 suspected ZIKV infections for an estimated incidence of 2.8 symptomatic cases per 1,000 persons per year. Our findings emphasize the continuing threat of ZIKV transmission in the setting of decreased surveillance and reporting.

Building the vector in: construction practices and the invasion and persistence of Anopheles stephensi in Jigjiga, Ethiopia.

Anopheles stephensi is a major vector of malaria in Asia and the Arabian Peninsula, and its recent invasion into Africa poses a major threat to malaria control and elimination efforts on the continent. The mosquito is well adapted to urban environments, and its presence in Africa could potentially lead to an increase in malaria transmission in cities. Most of the knowledge about An stephensi ecology in Africa has been generated from studies conducted during the rainy season, when vectors are most abundant. Here, we provide evidence from the peak of the dry season in the city of Jigjiga in Ethiopia, and report An stephensi immature stages infesting predominantly in water reservoirs made to support construction operations (ie, in construction sites or associated with brick-manufacturing businesses). Political and economic changes in Ethiopia (particularly the Somali Region) have fuelled an unprecedented construction boom since 2018 that, in our opinion, has been instrumental in the establishment, persistence, and propagation of An stephensi via the year-round availability of perennial larval habitats associated with construction. We argue that larval source management during the dry season might provide a unique opportunity for focused control of An stephensi in Jigjiga and similar areas.

Laboratory Evaluation of Efficacy of the Larvicide Spinosad Against AnophelesStephensi in Jigjiga, Ethiopia.

We report the efficacy of a commercial formulation of the insecticide spinosad against larvae of Anopheles stephensi populations found in the city of Jigjiga, Somali Region, eastern Ethiopia. Batches of 25 larvae (late III to early IV instars) collected from large water storage reservoirs associated with construction sites (the primary An. stephensi larval site in the dry season) were tested under laboratory conditions against each insecticide at a dose recommended by the manufacturer (Natular® G30, 0.02 g/5 liter), following World Health Organization guidelines. Mortality at 24-48 h postexposure was 100%. Results show that spinosad is effective against An. stephensi larvae and suggest that it may be a useful tool as part of larval source management plans aimed at controlling this invasive malaria vector in Ethiopia.

Targeted indoor residual insecticide applications shift Aedes aegypti age structure and arbovirus transmission potential.

While residual insecticide applications have the potential to decrease pathogen transmission by reducing the density of vectors and shifting the age structure of the adult mosquito population towards younger stages of development, this double entomological impact has not been documented for Aedes aegypti. Aedes collected from households enrolled in a cluster-randomized trial evaluating the epidemiological impact of targeted indoor residual spraying (TIRS) in Merida, Mexico, were dissected and their age structure characterized by the Polovodova combined with Christopher's ovariole growth methods. In total, 813 females were dissected to characterize age structure at 1, 3, 6, and 9 months post-TIRS. Significant differences in the proportion of nulliparous Ae. aegypti females between the treatment groups was found at one-month post-TIRS (control: 35% vs. intervention: 59%), three months (20% vs. 49%) but not at six or nine months post-TIRS. TIRS significantly shiftted Ae. aegypti age structure towards younger stages and led to a non-linear reduction in survivorship compared to the control arm. Reduced survivorship also reduced the number of arbovirus transmitting females (those who survived the extrinsic incubation period). Our findings provide strong evidence of the full entomological impact of TIRS, with important implications for quantifying the epidemiological impact of vector control methods.

Residual efficacy of the neonicotinoid insecticide clothianidin against pyrethroid-resistant Aedes aegypti.

BACKGROUND: Here we report the residual efficacy of the neonicotinoid insecticide clothianidin against pyrethroid-resistant Aedes aegypti. We first conducted a range-finding evaluation of clothianidin on three different substrates (wall, wood, cloth) using three doses (100, 300 and 600 mg a.i. m-2 ) and conducting World Health Organization (WHO) cone bioassays to assess acute (24 h) and delayed (up to 7 days) mortality. In experimental houses located in Merida (Mexico) and using free-flying pyrethroid-resistant Ae. aegypti females, we quantified the acute and delayed mortality after a 24-h exposure to the targeted indoor residual spraying (TIRS) of two clothianidin doses (100 and 300 mg a.i. m-2 ). RESULTS: Range-finding studies with WHO cones showed low (<50%) acute mortality for all surfaces, doses and times post spraying. Delayed mortality was higher, with average values above or close to the 60% mark (and 95% confidence interval estimates crossing 80% for the 600 mg a.i. m-2 dose). In experimental houses, a similar low acute mortality was quantified (range of mortality across 12 months was 2-44% for 100 mg a.i. m-2 and 8-61% for 300 mg a.i/m2 ). However, delayed mortality showed a strong effect of clothianidin on free-flying Ae. aegypti, with values above 80% up to 7 months post-TIRS. CONCLUSION: Novel residual insecticide molecules have a promising outlook for Ae. aegypti control and can contribute to the expansion and adoption of TIRS in urban areas. clothianidin can contribute to the control of resistant Ae. aegypti and provide residual control for up to 7 months after application. © 2022 Society of Chemical Industry.

Educational intervention for the control of Aedes aegypti with Wolbachia in Yucatan, Mexico.

The implementation of new control strategies for Aedes aegypti (Ae. Aegpyti), a vector of dengue, chikungunya, and Zika viruses, requires communities to adopt specific behaviors to achieve the success of these innovations. AIM: We evaluated the effect of an educational intervention based on the Precede-Proceed Model (PPM) and the Diffusion of Innovations Theory (DIT) for the control and prevention of diseases transmitted by Ae. aegypti through release of male mosquitoes infected with Wolbachia bacteria in a suburban town in Yucatan, Mexico. MATERIAL AND METHODS: From July 2019 to February 2020, a quasi-experimental study was carried out through an educational intervention (pre- and post-measurements) using quantitative-qualitative techniques, in a Yucatan suburban town where male mosquitoes with Wolbachia were released for the suppression of Ae. aegypti populations. Eleven educational workshops were attended by heads of household (n = 19) and schoolchildren (n = 11). Other 136 heads of household not attending the workshops received information individually. RESULTS: The educational intervention had a significant effect on the mean scores of the contributing and behavioral factors for adoption of innovation (p < 0.05) in the pre- and post-intervention measurements. CONCLUSION: Innovative methods for the control and prevention of diseases related to Aedes aegypti can be strengthened through educational interventions supported by sound methodologies. DESCRIPTORS: Community health education, Aedes aegypti, Wolbachia, Mexico.

Preventive residual insecticide applications successfully controlled Aedes aegypti in Yucatan, Mexico.

Insecticide-based approaches remain a key pillar for Aedes-borne virus (ABV, dengue, chikungunya, Zika) control, yet they are challenged by the limited effect of traditional outdoor insecticide campaigns responding to reported arboviral cases and by the emergence of insecticide resistance in mosquitoes. A three-arm Phase II unblinded entomological cluster randomized trial was conducted in Merida, Yucatan State, Mexico, to quantify the entomological impact of targeted indoor residual spraying (TIRS, application of residual insecticides in Ae. aegypti indoor resting sites) applied preventively 2 months before the beginning of the arbovirus transmission season. Trial arms involved the use of two insecticides with unrelated modes of action (Actellic 300CS, pirimiphos-methyl, and SumiShield 50WG, clothianidin) and a control arm where TIRS was not applied. Entomological impact was quantified by Prokopack adult collections performed indoors during 10 min per house. Regardless of the insecticide, conducting a preventive TIRS application led to significant reductions in indoor Ae. aegypti densities, which were maintained at the same levels as in the low arbovirus transmission period (Actellic 300CS reduced Ae. aegypti density up to 8 months, whereas SumiShield 50WG up to 6 months). The proportional reduction in Ae. aegypti abundance in treatment houses compared to control houses was 50-70% for Actellic 300CS and 43-63% for SumiShield 50WG. Total operational costs including insecticide ranged from US$4.2 to US$10.5 per house, depending on the insecticide cost. Conducting preventive residual insecticide applications can maintain Ae. aegypti densities at low levels year-round with important implications for preventing ABVs in the Americas and beyond.

Insecticide Susceptibility Tests of Aedes taeniorhynchus in Yucatan, Mexico.

We report results of susceptibility tests for Aedes taeniorhynchus from 2 localities of Yucatan State, Mexico, to different insecticides. The Centers for Disease Control and Prevention bottle bioassays were performed using the active ingredients of 3 pyrethroids, 2 organophosphates, and 1 carbamate: permethrin (15 µg/ml), deltamethrin (10 µg/ml), alpha-cypermethrin (10 µg/ml), malathion (50 µg/ml), chlorpyrifos (85 µg/ml), and bendiocarb (12.5 µg/ml). The mortality recorded at the diagnostic time of exposure (30 min) was 100% with all insecticides evaluated and for both populations. These results suggest complete susceptibility to the 3 chemical groups generally used for urban Ae. aegypti mosquito control.

Experimental evaluation of a metofluthrin passive emanator against Aedes albopictus.

BACKGROUND: With the recent occurrence of locally transmitted Aedes-borne viruses in the continental United States and Europe, and a lack of effective vaccines, new approaches to control Aedes aegypti and Aedes albopictus are needed. In sub-tropical urban settings in the US, Ae. albopictus is a dominant nuisance and arbovirus vector species. Unfortunately, the vector control toolbox against Ae. albopictus is not as well developed as for Ae. aegypti. Here, we evaluate the efficacy, longevity, and range of protectiveness of a novel passive metofluthrin emanator (10% active ingredient in a polyethylene mesh) against Ae. albopictus indoors and outdoors. METHODS: Four studies were conducted comparing the presence of the metofluthrin emanator to a control lacking emanator with interest in quantifying efficacy by human landing counts. Studies evaluated the effect of an emanator at varying distances from one or more human volunteers indoors and outdoors. Efficacy of emanators over time since activation was also evaluated. RESULTS: Mixed-effects models determined that sitting in close proximity to an emanator reduced landings by 89.5% outdoors and by 74.6% indoors. The emanator was determined protective when located immediately next to a human volunteer outdoors but not uniformly protective when located further away. The emanator was protective at all tested distances from the device indoors. Mortality of mosquitoes exposed to metofluthrin emanators was ~2x higher than those who were not exposed in indoor conditions. Finally, a Generalized Additive Model determined that emanators used continuously outdoors lost their effect after 2.5 weeks and stopped inducing paralysis in mosquitoes after 3.8 weeks of use. CONCLUSIONS: We show strong and lasting efficacy of 10% metofluthrin emanators against field Ae. albopictus both in indoor and outdoor conditions. Metofluthrin emanators can protect people from Ae. albopictus bites, representing a viable option for reducing human-mosquito contacts at home and beyond.

Pilot trial using mass field-releases of sterile males produced with the incompatible and sterile insect techniques as part of integrated Aedes aegypti control in Mexico.

BACKGROUND: The combination of Wolbachia-based incompatible insect technique (IIT) and radiation-based sterile insect technique (SIT) can be used for population suppression of Aedes aegypti. Our main objective was to evaluate whether open-field mass-releases of wAlbB-infected Ae. aegypti males, as part of an Integrated Vector Management (IVM) plan led by the Mexican Ministry of Health, could suppress natural populations of Ae. aegypti in urbanized settings in south Mexico. METHODOLOGY/PRINCIPAL FINDINGS: We implemented a controlled before-and-after quasi-experimental study in two suburban localities of Yucatan (Mexico): San Pedro Chimay (SPC), which received IIT-SIT, and San Antonio Tahdzibichén used as control. Release of wAlbB Ae. aegypti males at SPC extended for 6 months (July-December 2019), covering the period of higher Ae. aegypti abundance. Entomological indicators included egg hatching rates and outdoor/indoor adult females collected at the release and control sites. Approximately 1,270,000 lab-produced wAlbB-infected Ae. aegypti males were released in the 50-ha treatment area (2,000 wAlbB Ae. aegypti males per hectare twice a week in two different release days, totaling 200,000 male mosquitoes per week). The efficacy of IIT-SIT in suppressing indoor female Ae. aegypti density (quantified from a generalized linear mixed model showing a statistically significant reduction in treatment versus control areas) was 90.9% a month after initiation of the suppression phase, 47.7% two months after (when number of released males was reduced in 50% to match local abundance), 61.4% four months after (when initial number of released males was re-established), 88.4% five months after and 89.4% at six months after the initiation of the suppression phase. A proportional, but lower, reduction in outdoor female Ae. aegypti was also quantified (range, 50.0-75.2% suppression). CONCLUSIONS/SIGNIFICANCE: Our study, the first open-field pilot implementation of Wolbachia IIT-SIT in Mexico and Latin-America, confirms that inundative male releases can significantly reduce natural populations of Ae. aegypti. More importantly, we present successful pilot results of the integration of Wolbachia IIT-SIT within a IVM plan implemented by Ministry of Health personnel.

SARS-CoV-2 antibody prevalence in a pediatric cohort of unvaccinated children in Mérida, Yucatán, México.

The prevalence of SARS-CoV-2 exposure in children during the global COVID-19 pandemic has been underestimated due to lack of testing and the relatively mild symptoms in adolescents. Understanding the exposure rates in the pediatric population is essential as children are the last to receive vaccines and can act as a source for SARS-CoV-2 mutants that may threaten vaccine escape. This cross-sectional study aims to quantify the prevalence of anti-SARS-CoV-2 serum antibodies in children in a major city in México in the Spring of 2021 and determine if there are any demographic or socioeconomic correlating factors. We obtained socioeconomic information and blood samples from 1,005 children from 50 neighborhood clusters in Mérida, Yucatán, México. We then tested the sera of these participants for anti-SARS-CoV-2 IgG and IgM antibodies using lateral flow immunochromatography. We found that 25.5% of children in our cohort were positive for anti-SARS-CoV-2 antibodies and there was no correlation between age and antibody prevalence. Children that lived with large families were statistically more likely to have antibodies against SARS-CoV-2. Spatial analyses identified two hotspots of high SARS-CoV-2 seroprevalence in the west of the city. These results indicate that a large urban population of unvaccinated children has been exposed to SARS-CoV-2 and that a major correlating factor was the number of people within the child's household with a minor correlation with particular geographical hotspots. There is also a larger population of children that may be susceptible to future infection upon easing of social distancing measures. These findings suggest that in future pandemic scenarios, limited public health resources can be best utilized on children living in large households in urban areas.

Mosquito species (Diptera: culicidae) collected after tropical storm cristobal in Merida, Yucatan, South-east Mexico.

After the tropical storm Cristobal, we performed special adult entomological collections in the peri-domicile of 35 houses from 25 neighborhoods of Mérida, Yucatan, Mexico in response to complaints from the community about an increased nuisance due to an abundance of mosquitoes. A total of 1,275 specimens from four genera and 13 species were collected: Aedes taeniorhynchus (92%), Culex quinquefasciatus (72%), Aedes aegypti (72%), Psorophora mexicana (36%), Psorophora cyanescens (32%), Aedes scapularis (24%), Culex nigripalpus (24%), Aedes albopictus (8%), Psorophora ferox (4%), Haemagogus equinus (4%), Aedes trivittatus (4%), Culex coronator (4%), Culex iolambdis (4%). From these collections, the increased mosquito nuisance was mainly the result of invasive species such as Aedes taeniorhynchus and Psorophora. City wide, vehicle mounted ULV spraying was performed by the MoH and the municipality of Merida to control adult mosquito populations. We report Culex iolambdis for the first time in Merida and Psorophora mexicana for the state of Yucatan.

Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti.

BACKGROUND: There is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS. METHODS: We evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify "delayed mortality". RESULTS: Mean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80-97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months). CONCLUSIONS: Chlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.

Protective effect of house screening against indoor Aedes aegypti in Mérida, Mexico: A cluster randomised controlled trial.

OBJECTIVE: To evaluate the protective effect of house screening (HS) on indoor Aedes aegypti infestation, abundance and arboviral infection in Merida, Mexico. METHODS: In 2019, we performed a cluster randomised controlled trial (6 control and 6 intervention areas: 100 households/area). Intervention clusters received permanently fixed fiberglass HS on all windows and doors. The study included two cross-sectional entomologic surveys, one baseline (dry season in May 2019) and one post-intervention (PI, rainy season between September and October 2019). The presence and number of indoor Aedes females and blood-fed females (indoor mosquito infestation) as well as arboviral infections with dengue (DENV) and Zika (ZIKV) viruses were evaluated in a subsample of 30 houses within each cluster. RESULTS: HS houses had significantly lower risk for having Aedes aegypti female mosquitoes (odds ratio [OR] = 0.56, 95% CI 0.33-0.97, p = 0.04) and blood-fed females (OR = 0.53, 95% CI 0.28-0.97, p = 0.04) than unscreened households from the control arm. Compared to control houses, HS houses had significantly lower indoor Ae. aegypti abundance (rate ratio [RR] = 0.50, 95% CI 0.30-0.83, p = 0.01), blood-fed Ae. aegypti females (RR = 0.48, 95% CI 0.27-0.85, p = 0.01) and female Ae. aegypti positive for arboviruses (OR = 0.29, 95% CI 0.10-0.86, p = 0.02). The estimated intervention efficacy in reducing Ae. aegypti arbovirus infection was 71%. CONCLUSIONS: These results provide evidence supporting the use of HS as an effective pesticide-free method to control house infestations with Aedes aegypti and reduce the transmission of Aedes-transmitted viruses such as DENV, chikungunya (CHIKV) and ZIKV.

Identifying urban hotspots of dengue, chikungunya, and Zika transmission in Mexico to support risk stratification efforts: a spatial analysis.

BACKGROUND: Effective Aedes aegypti control is limited, in part, by the difficulty in achieving sufficient intervention coverage. To maximise the effect of vector control, areas with persistently high numbers of Aedes-borne disease cases could be identified and prioritised for preventive interventions. We aimed to identify persistent Aedes-borne disease hotspots in cities across southern Mexico. METHODS: In this spatial analysis, geocoded cases of dengue, chikungunya, and Zika from nine endemic Mexican cities were aggregated at the census-tract level. We included cities that were located in southern Mexico (the arbovirus endemic region of Mexico), with a high burden of dengue cases (ie, more than 5000 cases reported during a 10-year period), and listed as high priority for the Mexican dengue control and prevention programme. The Getis-Ord Gi*(d) statistic was applied to yearly slices of the dataset to identify spatial hotspots of each disease in each city. We used Kendall's W coefficient to quantify the agreement in the distribution of each virus. FINDINGS: 128 507 dengue, 4752 chikungunya and 25 755 Zika clinical cases were reported between Jan 1, 2008, and Dec 31, 2016. All cities showed evidence of transmission heterogeneity, with a mean of 17·6% (SD 4·7) of their total area identified as persistent disease hotspots. Hotspots accounted for 25·6% (SD 9·7; range 12·8-43·0) of the population and 32·1% (10·5; 19·6-50·5) of all Aedes-borne disease cases reported. We found an overlap between hotspots of 61·7% for dengue and Zika and 53·3% for dengue and chikungunya. Dengue hotspots in 2008-16 were significantly associated with dengue hotspots detected during 2017-20 in five of the nine cities. Heads of vector control confirmed hotspot areas as problem zones for arbovirus transmission. INTERPRETATION: This study provides evidence of the overlap of Aedes-borne diseases within geographical hotspots and a methodological framework for the stratification of arbovirus transmission risk within urban areas, which can guide the implementation of surveillance and vector control. FUNDING: USAID, the US Centers for Disease Control and Prevention, the Canadian Institutes of Health Research, International Development Research Centre, Fondo Mixto CONACyT (Mexico)-Gobierno del Estado de Yucatan, and the US National Institutes of Health. TRANSLATION: For the Spanish translation of the abstract see Supplementary Materials section.

Abundance and Seasonality of Aedes aegypti (Diptera: Culicidae) in Two Suburban Localities of South Mexico, With Implications for Wolbachia (Rickettsiales: Rickettsiaceae)-Carrying Male Releases for Population Suppression.

We conducted a baseline characterization of the abundance and seasonality of Aedes aegypti (Linnaeus, 1762)-a vector of dengue, chikungunya, and Zika-in two suburban localities of Yucatan, Mexico, as the first step in the implementation of an integrated vector management (IVM) plan combining 'traditional Aedes control' (source reduction/truck-mounted ultra-low volume [ULV] spraying) and incompatible insect technique/sterile insect technique for population suppression in Yucatan, Mexico. Weekly entomological collections with ovitraps and BG-sentinel traps were performed in 1-ha quadrants of both localities for 1 yr. Three distinct periods/phases were identified, closely associated with precipitation: 1) a phase of low population abundance during the dry season (weekly average of Aedes eggs per ovitrap and adults per BG trap = 15.51 ± 0.71 and 10.07 ± 0.88, respectively); 2) a phase of population growth and greatest abundance of Aedes (49.03 ± 1.48 eggs and 25.69 ± 1.31 adults) during the rainy season; and finally 3) a phase of decline among populations (20.91 ± 0.97 eggs and 3.24 ± 0.21 adults) after the peak of the rainy season. Seasonal abundance and dynamics of Ae. aegypti populations suggest that it is feasible to develop and implement time-specific actions as part of an IVM approach incorporating integrating novel technologies (such as rear-and-release of Wolbachia-infected males) with classic (insecticide-based) approaches implemented routinely for vector control. In agreement with the local vector control program, we propose a pilot IVM strategy structured in a preparation phase, an attack phase with traditional vector control, and a suppression phase with inundative releases, which are described in this paper.

Detection of Aedes (Stegomyia) albopictus (Skuse) in ovitraps of Mérida city, México / Detección de Aedes (Stegomyia) albopictus (Skuse) en ovitrampas en Mérida, México

Introduction: The vector-borne diseases program in México has an established network of ovitraps for entomological surveillance of Aedes spp. In response to reports of Aedes albopictus in the periphery of Mérida, the state capital of Yucatán, the Ministry of Health increased the specificity of this surveillance. Objective: To describe the presence and distribution of Ae. albopictus in Mérida and its relative abundance compared to Aedes aegypti in ovitraps of the vector control program. Materials and methods: During October, 2019, 91 ovitraps were randomly selected from 31 neighborhoods of Mérida. Mosquitoes were reared at the insectary of the Collaborative Unit for Entomological Bioassays of the Autonomous University of Yucatán from eggs collected in the field. Relative abundance was determined for adult individuals of each identified species and neighborhood. Results: 32 % of the neighborhoods were positive for Ae. albopictus and 100 % for Ae. aegypti. A total of 28 adults of Ae. albopictus (10 females and 18 males) were obtained from ovitraps. No correlation was observed between the abundance of Ae. aegypti and Ae. albopictus for both adults and females (p>0.05) at the neighborhood level. Conclusions: The results confirm that Ae. albopictus coexisted with Ae. aegypti in Mérida at the time of the study. The low relative abundance suggests that Ae. albopictus was in the initial phase of invasion.

Introducción. El programa de enfermedades transmitidas por vectores en México tiene una red establecida de ovitrampas para la vigilancia entomológica de Aedes spp. Los servicios de salud del estado de Yucatán, en respuesta a reportes de Aedes albopictus en la periferia de Mérida, capital del estado, incrementaron la especificidad de dicha vigilancia. Objetivo. Describir la presencia y distribución de Ae. albopictus en Mérida y su abundancia relativa comparada con Aedes aegypti, en ovitrampas del programa de control de vectores. Materiales y métodos. Durante octubre de 2019, se seleccionaron al azar 91 ovitrampas en 31 barrios de Mérida. Los mosquitos adultos se obtuvieron del insectario de la Unidad Colaborativa para Bioensayos Entomológicos de la Universidad Autónoma de Yucatán a partir de huevos recolectados en campo. Se determinó la abundancia relativa de individuos adultos de cada especie identificada y por barrios evaluados. Resultados. En el 32 % de los barrios muestreados, se detectó Ae. albopictus y, en todos ellos, Ae. aegypti. Se recolectaron 28 adultos de Ae. albopictus (10 hembras y 18 machos) en las ovitrampas. No se observó correlación entre la abundancia de adultos ni de hembras Ae. aegypti y Ae. albopictus por barrio (p>0,05). Conclusiones. Los resultados confirmaron que Ae. albopictus estaba coexistiendo con Ae. aegypti en Mérida en el momento del estudio. La baja abundancia relativa sugiere que Ae. albopictus se encontraba en la fase inicial de invasión.

Detección de Aedes (Stegomyia) albopictus (Skuse) en ovitrampas en Mérida, México / Detection of Aedes (Stegomyia) albopictus (Skuse) in ovitraps of Mérida city, México

Resumen | Introducción. El programa de enfermedades transmitidas por vectores en México tiene una red establecida de ovitrampas para la vigilancia entomológica de Aedes spp. Los servicios de salud del estado de Yucatán, en respuesta a reportes de Aedes albopictus en la periferia de Mérida, capital del estado, incrementaron la especificidad de dicha vigilancia. Objetivo. Describir la presencia y distribución de Ae. albopictus en Mérida y su abundancia relativa comparada con Aedes aegypti, en ovitrampas del programa de control de vectores. Materiales y métodos. Durante octubre de 2019, se seleccionaron al azar 91 ovitrampas en 31 barrios de Mérida. Los mosquitos adultos se obtuvieron del insectario de la Unidad Colaborativa para Bioensayos Entomológicos de la Universidad Autónoma de Yucatán a partir de huevos recolectados en campo. Se determinó la abundancia relativa de individuos adultos de cada especie identificada y por barrios evaluados. Resultados. En el 32 % de los barrios muestreados, se detectó Ae. albopictus y, en todos ellos, Ae. aegypti. Se recolectaron 28 adultos de Ae. albopictus (10 hembras y 18 machos) en las ovitrampas. No se observó correlación entre la abundancia de adultos ni de hembras Ae. aegypti y Ae. albopictus por barrio (p>0,05). Conclusiones. Los resultados confirmaron que Ae. albopictus estaba coexistiendo con Ae.aegypti en Mérida en el momento del estudio. La baja abundancia relativa sugiere que Ae.albopictus se encontraba en la fase inicial de invasión.

Abstract | Introduction:The vector-borne diseases program in México has an established network of ovitraps for entomological surveillance of Aedes spp. In response to reports of Aedes albopictus in the periphery of Mérida, the state capital of Yucatán, the Ministry of Health increased the specificity of this surveillance. Objective: To describe the presence and distribution of Ae. albopictus in Mérida and its relative abundance compared to Aedesaegypti in ovitraps of the vector control program. Materials and methods: During October, 2019, 91 ovitraps were randomly selected from 31 neighborhoods of Mérida. Mosquitoes were reared at the insectary of the Collaborative Unit for Entomological Bioassays of the Autonomous University of Yucatán from eggs collected in the field. Relative abundance was determined for adult individuals of each identified species and neighborhood. Results: 32 % of the neighborhoods were positive for Ae. albopictus and 100 % for Ae. aegypti. A total of 28 adults of Ae. albopictus (10 females and 18 males) were obtained from ovitraps. No correlation was observed between the abundance of Ae. aegypti and Ae. albopictus for both adults and females (p>0.05) at the neighborhood level. Conclusions: The results confirm that Ae. albopictus coexisted with Ae. aegypti in Mérida at the time of the study. The low relative abundance suggests that Ae. albopictus was in the initial phase of invasion.

The entomological impact of passive metofluthrin emanators against indoor Aedes aegypti: A randomized field trial.

BACKGROUND: In the absence of vaccines or drugs, insecticides are the mainstay of Aedes-borne disease control. Their utility is challenged by the slow deployment of resources, poor community compliance and inadequate household coverage. Novel application methods are required. METHODOLOGY AND PRINCIPAL FINDINGS: A 10% w/w metofluthrin "emanator" that passively disseminates insecticide from an impregnated net was evaluated in a randomized trial of 200 houses in Mexico. The devices were introduced at a rate of 1 per room and replaced at 3-week intervals. During each of 7 consecutive deployment cycles, indoor resting mosquitoes were sampled using aspirator collections. Assessments of mosquito landing behaviours were made in a subset of houses. Pre-treatment, there were no differences in Aedes aegypti indices between houses recruited to the control and treatment arms. Immediately after metofluthrin deployment, the entomological indices between the trial arms diverged. Averaged across the trial, there were significant reductions in Abundance Rate Ratios for total Ae. aegypti, female abundance and females that contained blood meals (2.5, 2.4 and 2.3-times fewer mosquitoes respectively; P<0.001). Average efficacy was 60.2% for total adults, 58.3% for females, and 57.2% for blood-fed females. The emanators also reduced mosquito landings by 90% from 12.5 to 1.2 per 10-minute sampling period (P<0.05). Homozygous forms of the pyrethroid resistant kdr alleles V410L, V1016L and F1534C were common in the target mosquito population; found in 39%, 24% and 95% of mosquitoes collected during the trial. CONCLUSIONS/SIGNIFICANCE: This is the first randomized control trial to evaluate the entomological impact of any volatile pyrethroid on urban Ae. aegypti. It demonstrates that volatile pyrethroids can have a sustained impact on Ae. aegypti population densities and human-vector contact indoors. These effects occur despite the presence of pyrethroid-resistant alleles in the target population. Formulations like these may have considerable utility for public health vector control responses.