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Triatoma dimidiata, the main vector of Trypanosoma cruzi throughout South Mexico and Central America, infest domiciles and peridomestic ecotopes of rural and semi-rural communities. This study reports the effect of the residual application of the organophosphate pirimiphos-methyl in a microencapsulated formulation (Actellic 300CS) for the control of intradomiciliary and peridomestic T. dimidiata in the community of Tekik de Regil (hereafter Tekik) in Yucatan, Southeast Mexico. From March to October 2022, a two-arm, unblinded entomological trial was performed in Tekik. Timed Manual Collections (TMC) characterized house and peridomicile infestation by T. dimidiata prior (baseline) and after the residual spraying (RS) (post-intervention) of a microencapsulated formulation. A total of 120 premises were surveyed (60 positive and 60 negative for T. dimidiata), randomly allocated 1:1 to treatment (RS with Actellic 300CS) and control (no RS) arms. Monthly post-spraying entomological surveys (May-October) with TMC were carried out in a random sample of ten houses from each arm. We analyzed the association between the treatment and post-intervention infestations using chi-square contingency tables. The estimated efficacy of the intervention with the 95% Confidence Intervals (CI) was calculated with the efficacy formula, using the Odds Ratio (OD) calculated from a binomial Generalized Linear Mixed Model (GLMM) from the positive premises in the baseline survey and post-intervention, using time as a random effect. Domestic infestations post-intervention were only detected in the control group (2/60 houses, 3.3%). Cumulative peridomestic infestation was significantly higher in the control arm (31.7%; 19/60) compared to the treatment arm (11.7%; 7/60) (X2 = 0.007, p < 0.01). The cumulative 6-month estimated efficacy of the intervention (% reduction in treatment versus control arm) was 65% (95% CI: 14%-79%). A single application of Actellic 300CS reduced T. dimidiata infestations by more than 60% for up to 6 months and provides evidence of an alternative formulation suitable for triatomine control in Mexico.

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.

The operational impact of deltamethrin resistance on the efficacy of indoor insecticide applications to control Aedes aegypti was evaluated in Merida, Mexico. A randomized controlled trial quantified the efficacy of indoor residual spraying (IRS) against adult Ae. aegypti in houses treated with either deltamethrin (to which local Ae. aegypti expressed a high degree of resistance) or bendiocarb (to which local Ae. aegypti were fully susceptible) as compared to untreated control houses. All adult Ae. aegypti infestation indices during 3 months post-spraying were significantly lower in houses treated with bendiocarb compared to untreated houses (odds ratio <0.75; incidence rate ratio < 0.65) whereas no statistically significant difference was detected between the untreated and the deltamethrin-treated houses. On average, bendiocarb spraying reduced Ae. aegypti abundance by 60% during a 3-month period. Results demonstrate that vector control efficacy can be significantly compromised when the insecticide resistance status of Ae. aegypti populations is not taken into consideration.

There is a need for effective methods to control Aedes aegypti and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact. A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012-2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of Ae. aegypti adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of Ae. aegypti female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with ~70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation. The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of Ae. aegypti. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted and therefore recommended.

Background Current urban vector control strategies have failed to contain dengue epidemics and to prevent the global expansion of Aedes -borne viruses (ABVs: dengue, chikungunya, Zika). Part of the challenge in sustaining effective ABV control emerges from the paucity of evidence regarding the epidemiological impact of any Aedes control method. A strategy for which there is limited epidemiological evidence is targeted indoor residual spraying (TIRS). TIRS is a modification of classic malaria indoor residual spraying that accounts for Aedes aegypti resting behavior by applying residual insecticides on exposed lower sections of walls (< 1.5 m), under furniture, and on dark surfaces. Methods/design We are pursuing a two-arm, parallel, unblinded, cluster randomized controlled trial to quantify the overall efficacy of TIRS in reducing the burden of laboratory-confirmed ABV clinical disease (primary endpoint). The trial will be conducted in the city of Merida, Yucatan State, Mexico (population ~ 1million), where we will prospectively follow 4600 children aged 2–15 years at enrollment, distributed in 50 clusters of 5 × 5 city blocks each. Clusters will be randomly allocated ( n  = 25 per arm) using covariate-constrained randomization. A “fried egg” design will be followed, in which all blocks of the 5 × 5 cluster receive the intervention, but all sampling to evaluate the epidemiological and entomological endpoints will occur in the “yolk,” the center 3 × 3 city blocks of each cluster. TIRS will be implemented as a preventive application (~ 1–2 months prior to the beginning of the ABV season). Active monitoring for symptomatic ABV illness will occur through weekly household visits and enhanced surveillance. Annual sero-surveys will be performed after each transmission season and entomological evaluations of Ae. aegypti indoor abundance and ABV infection rates monthly during the period of active surveillance. Epidemiological and entomological evaluation will continue for up to three transmission seasons. Discussion The findings from this study will provide robust epidemiological evidence of the efficacy of TIRS in reducing ABV illness and infection. If efficacious, TIRS could drive a paradigm shift in Aedes control by considering Ae. aegypti behavior to guide residual insecticide applications and changing deployment to preemptive control (rather than in response to symptomatic cases), two major enhancements to existing practice. Trial registration ClinicalTrials.gov NCT04343521 . Registered on 13 April 2020. The protocol also complies with the WHO International Clinical Trials Registry Platform (ICTRP) (Additional file 1). Primary sponsor National Institutes of Health, National Institute of Allergy and Infectious Diseases (NIH/NIAID).

A cluster-randomized controlled trial quantified the entomological efficacy of aerial ultra-low volume (AULV) applications of the insecticide chlorpyrifos against Aedes aegypti in Puerto Vallarta, México, during November–October 2017. The trial involved 16 large (1 × 1 km) clusters distributed between treatment-control arms. Primary endpoint was the abundance of Ae. aegypti indoors (total adults, females, and blood-fed females) collected using Prokopack aspirators. After four consecutive weekly cycles of AULV, all adult Ae. aegypti infestation indices were significantly lower in the treatment arm (OR and IRR ≤ 0.28). Efficacy in reducing indoor Ae. aegypti increased with each weekly application cycle from 30 to 73% (total adults), 33 to 76% (females), and 45.5 to 89% (blood-fed females). Entomological indices remained significantly lower in the treatment arm up to 2 wk after the fourth spraying round. Performing AULV spraying can have significant and lasting entomological impact on Ae. aegypti as long as multiple (ideally four) spray cycles are implemented using an effective insecticide.

Targeted indoor residual spraying focuses insecticide applications on common resting surfaces of mosquitoes (an arboviral disease vector) in houses, such as exposed lower sections of walls and under furniture. We conducted a two-group, parallel, unblinded, cluster-randomized trial in Merida, Mexico, to quantify the efficacy of targeted indoor residual spraying for preventing aedes-borne diseases (chikungunya, dengue, or Zika). Children 2 to 15 years of age were enrolled from households in 50 clusters of five-by-five city blocks. Households in 25 clusters received an annual application of targeted indoor residual spraying (intervention) before each season of aedes-borne disease (July through December). All clusters received routine Ministry of Health vector control. The primary end point was laboratory-confirmed, symptomatic aedes-borne disease. Community effects were assessed with the use of geolocated national surveillance data. A total of 4461 children were monitored for up to three seasons (2021, 2022, and 2023). The indoor density of mosquitoes was 59% (95% confidence interval [CI], 51 to 65) lower with the intervention than with control. A total of 422 cases of aedes-borne disease were confirmed, primarily dengue in 2023. In the per-protocol analysis of cluster centers, 91 cases occurred among 1038 participants in the intervention group and 89 cases among 1037 participants in the control group (efficacy, -12.8%; 95% CI, -60.7 to 23.0). In an intention-to-treat analysis of entire clusters, 198 cases occurred among 2239 participants in the intervention group and 199 cases among 2222 participants in the control group (efficacy, 3.9%; 95% CI, -28.1 to 26.7). Adjustment of analyses for mobility or demographic characteristics did not change results. On the basis of 150 cases in the intervention clusters and 202 in the control clusters that were geolocated, the estimated community effect of the intervention was 24.0% (95% CI, 6.0 to 38.6). Two cases of multisymptom adverse events (e.g., nausea, watery eyes, diarrhea, and vomiting) were associated with the intervention. Despite lower entomologic indexes with targeted indoor residual spraying than with routine vector control, the cumulative incidence of aedes-borne diseases was not significantly lower with targeted indoor residual spraying. (Funded by the National Institutes of Health and the Innovative Vector Control Consortium; ClinicalTrials.gov number, NCT04343521.).

Nadia A Fernández-Santos,1,2,* Mario A Rodríguez-Pérez,1,* Sofía Segovia-Mancillas,1,3,* Luis L Rodríguez,4 Sarah A Hamer,5 Gabriel L Hamer,2 Fabián Correa-Morales,6 Susano Medina-Jaramillo,7 Maria Gabriela Palacios-Mendoza,8 Epigmenio Cruz-Aldán,9 Gabriela del Carmen Rodriguez-Dominguez,10 Carlos H Gomez-Hernandez,10 Arturo Larraga-Guillén,11 Irene López González,11 Luis M Rodríguez-Martínez,12 Aldo I Ortega-Morales,13 Ma Isabel Salazar,14 Héctor Enrique Valdez-Gómez,11 Miguel A Márquez Ruiz,15 Maria J Perteguer,16 Benjamín Gastón Gómez-Gordillo,17 Jesús A Aguilar-Durán,1 Ingeborg D Becker Fauser,18 Scott C Weaver,19 Michael J Turell,20 Laura D Kramer,21,* Jose Guillermo Estrada-Franco1,* 1Instituto Politécnico Nacional, Centro de Biotecnología Genómica, Reynosa, Tamaulipas, Mexico; 2Department of Entomology, Texas A&M University, College Station, TX, USA; 3Facultad de Medicina, Universidad México Americana del Norte, Reynosa, Tamaulipas, Mexico; 4Foreign Animal Disease Research Unit, USDA/ARS Plum Island Animal Disease Center, Greenport, NY, USA; 5Department of Veterinary Integrative Biosciences, College Station, TX, USA; 6Centro Nacional de Programas Preventivos y Control de Enfermedades, Secretaría de Salud, Ciudad de México, Mexico; 7Academia Veterinaria Mexicana, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; 8Zoologico Miguel Alvarez del Toro (ZOOMAT), Tuxtla Gutierrez, Chiapas, Mexico; 9Programas Ambientales Grupo Libera, Merida, Yucatán, Mexico; 10Laboratorio Estatal de Salud, Secretaria de Salud de Chiapas, Tuxtla Gutierrez, Chiapas, Mexico; 11CPA-SENASICA, Comisión México-Estados Unidos para la Prevención de la Fiebre Aftosa y otras Enfermedades Exóticas de los Animales, Ciudad de México, Mexico; 12Centro de Estudios e Investigaciones Interdisciplinarios, Universidad Autónoma de Coahuila, Saltillo, Coahuila, Mexico; 13Universidad Autónoma Agraria Antonio Narro Unidad Laguna, Torreón, Coahuila, Mexico; 14Laboratorio Nacional de Vacunología y Virus Tropicales, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de México, Mexico; 15Departamento de Postgrado en Medicina Aviar, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad de México, Mexico; 16Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain; 17Comisión Nacional de Áreas Naturales Protegidas (CONANP), Palacio Federal 3er. Piso, Segunda Oriente-Norte, Tuxtla Gutiérrez, Chiapas, C.P. 29000, Mexico; 18Universidad Nacional Autónoma de México, Facultad de Medicina, Departamento de Medicina Experimental, Hospital General de México, Ciudad de México, Mexico; 19World Reference Center for Emerging Viruses and Arboviruses, Institute for Human Infections and Immunity, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, USA; 20VectorID LLC, Frederick, MD, USA; 21School of Public Health, University of the State of New York at Albany, Albany, NY, USA*These authors contributed equally to this workCorrespondence: Jose Guillermo Estrada-Franco, Instituto Politécnico Nacional, Centro de Biotecnología Genómica, Reynosa, Tamaulipas, Mexico, Tel +525534535428, Email jestradaf@ipn.mx Laura D Kramer, School of Public Health, University of the State of New York at Albany, Albany, NY, USA, Tel +15183222706, Email ldkculex@gmail.comAbstract: Zoonotic pathogens such as arboviruses, arenaviruses, filoviruses, coronaviruses, highly pathogenic Avian Influenza A (H5N1) viruses, vesiculoviruses, and many others are emerging and reemerging worldwide, jeopardizing global veterinary and public health. Parasitic diseases such as visceral and cutaneous leishmaniasis, trypanosomiasis (Trypanosoma cruzi), myiasis, and river blindness (Onchocerca volvulus) are also paramount for public health in the Americas and elsewhere. In the fall 2024, a group of experts convened in Chiapas, Mexico, for the Fourth Mesoamerican Symposium “Dr. Roberto Navarro López” on Arboviruses and Emerging Zoonotic Diseases. Here, we highlight the importance of some zoonotic pathogens and parasites affecting human health that are being impacted by anthropogenic activities. In this context, there are drivers such as changes in climate and landscape transformations, unsound agricultural practices, and wildlife niche replacement delivering numerous opportunities for zoonotic pathogens to emerge and threaten human health and food security.Keywords: zoonosis, arboviruses, emerging diseases, re-emerging diseases, symposium, training course

Zika virus (ZIKV) is a mosquito-borne pathogen, and Aedes aegypti has been identified as the main vector of the disease. Other mosquito species in the Aedes and Culex genera have been suggested to have the potential for being competent vectors based on experimental exposition of mosquitoes to an infectious blood meal containing ZIKV. Here, we report the isolation in cell culture of ZIKV obtained from different body parts of wild-caught female mosquitoes ( Ae . aegypti , Ae . vexans , Cx . quinquefasciatus , Cx . coronator , and Cx . tarsalis ) and whole male mosquitoes ( Ae . aegypti and Cx . quinquefasciatus ) in Mexico. Importantly, this is the first report that shows the presence of the virus in the salivary glands of the wild-caught female mosquitoes species, Cx . coronator , Cx . tarsalis , and Ae . vexans . Our findings strongly suggest that all the species reported herein are potential vectors for ZIKV.

Response to Zika virus (ZIKV) invasion in Brazil lagged a year from its estimated February 2014 introduction, and was triggered by the occurrence of severe congenital malformations. Dengue (DENV) and chikungunya (CHIKV) invasions tend to show similar response lags. We analyzed geo-coded symptomatic case reports from the city of Merida, Mexico, with the goal of assessing the utility of historical DENV data to infer CHIKV and ZIKV introduction and propagation. About 42% of the 40,028 DENV cases reported during 2008-2015 clustered in 27% of the city, and these clustering areas were where the first CHIKV and ZIKV cases were reported in 2015 and 2016, respectively. Furthermore, the three viruses had significant agreement in their spatio-temporal distribution (Kendall W>0.63; p<0.01). Longitudinal DENV data generated patterns indicative of the resulting introduction and transmission patterns of CHIKV and ZIKV, leading to important insights for the surveillance and targeted control to emerging Aedes-borne viruses.