A prospective cohort study to evaluate peridomestic infection as a determinant of dengue transmission: Protocol

<p>Abstract</p> <p>Background</p> <p>Vector control programs, which have focused mainly on the patient house and peridomestic areas around dengue cases, have not produced the expected impact on transmission. This project will evaluate the assumption that the endemic/epidemic transmission of dengue begins around peridomestic vicinities of the primary cases. Its objective is to assess the relationship between symptomatic dengue case exposure and peridomestic infection incidence.</p> <p>Methods/Design</p> <p>A prospective cohort study will be conducted (in Tepalcingo and Axochiapan, in the state of Morelos, Mexico), using the state surveillance system for the detection of incident cases. Paired blood specimens will be collected from both the individuals who live with the incident cases and a sample of subjects residing within a 25-meter radius of such cases (exposed cohort), in order to measure dengue-specific antibodies. Other subjects will be selected from areas which have not presented any incident cases within 200 meters, during the two months preceding the sampling (non-exposed cohort). Symptomatic/asymptomatic incident infection will be considered as the dependent variable, exposure to confirmed dengue cases, as the principal variable, and the socio-demographic, environmental and socio-cultural conditions of the subjects, as additional explanatory variables.</p> <p>Discussion</p> <p>Results indicating a high infection rate among the exposed subjects would justify the application of peridomestic control measures and call for an evaluation of alternate causes for insufficient program impact. On the other hand, a low incidence of peridomestic-infected subjects would support the hypothesis that infection occurs outside the domicile, and would thus explain why the vector control measures applied in the past have exerted such a limited impact on cases incidence rates. The results of the present study may therefore serve to reassess site selection for interventions of this type.</p

Field Effectiveness of Drones to Identify Potential Aedes aegypti Breeding Sites in Household Environments from Tapachula, a Dengue-Endemic City in Southern Mexico

Aedes aegypti control programs require more sensitive tools in order to survey domestic and peridomestic larval habitats for dengue and other arbovirus prevention areas. As a consequence of the COVID-19 pandemic, field technicians have faced a new occupational hazard during their work activities in dengue surveillance and control. Safer strategies to monitor larval populations, in addition to minimum householder contact, are undoubtedly urgently needed. Drones can be part of the solution in urban and rural areas that are dengue-endemic. Throughout this study, the proportion of larvae breeding sites found in the roofs and backyards of houses were assessed using drone images. Concurrently, the traditional ground field technician’s surveillance was utilized to sample the same house groups. The results were analyzed in order to compare the effectiveness of both field surveillance approaches. Aerial images of 216 houses from El Vergel village in Tapachula, Chiapas, Mexico, at a height of 30 m, were obtained using a drone. Each household was sampled indoors and outdoors by vector control personnel targeting all the containers that potentially served as Aedes aegypti breeding sites. The main results were that the drone could find 1 container per 2.8 found by ground surveillance; however, containers that were inaccessible by technicians in roofs and backyards, such as plastic buckets and tubs, disposable plastic containers and flowerpots were more often detected by drones than traditional ground surveillance. This new technological approach would undoubtedly improve the surveillance of Aedes aegypti in household environments, and better vector control activities would therefore be achieved in dengue-endemic countries

Gender-related family head schooling and Aedes aegypti larval breeding risk in Southern Mexico Escolaridad con relación al género de los jefes de familia y el riesgo de cría de Aedes aegypti en el sur de México

Objective. To investigate if family head genre-associated education is related to the risk of domiciliary Aedes aegypti larval breeding in a dengue-endemic village of Southern Mexico. Material and Methods. A family head was considered to have a low education level if he/she had not completed elementary school. To estimate larval breeding risk within each household, a three-category Maya index was constructed using a weighted estimation of controllable and disposable domestic water containers. A socio-economic index was constructed based on household construction characteristics. Results. Low-level education of either family head was associated to higher larval breeding risk. Households with low-educated mothers had more larval breeding containers. These associations persisted after adjusting for household socio-economic level. Conclusions. These results indicate that households with female family heads with low education levels accumulate more containers that favor Ae. aegypti breeding, and that education campaigns for dengue control should be addressed to this part of the population.Objetivo. Investigar si la escolaridad asociada con el género de los jefes de familia de una localidad endémica de dengue en el sur de México estaba relacionada con el riesgo de cría intradomiciliaria de Aedes aegypti. Material y métodos. Se consideró que un jefe de familia tenía baja educación si él/ella no había completado la educación primaria. Para estimar el riesgo de cría larvaria en cada domicilio se construyó un Indice Maya de tres categorías a partir de la estimación ponderada de recipientes controlables y desechables. Se construyó un índice socioeconómico basado en los materiales de construcción de la casa. Resultados. Niveles bajos de educación de los jefes de familia se asociaron con niveles altos de riesgo de cría de larvas de mosquitos. Pero las casas con jefas de familia con baja educación tuvieron más recipientes en riesgo para la cría de larvas. Estas observaciones no se modificaron después de ajustar por el nivel socioeconómico. Conclusiones. Estos resultados indican que las casas con jefas de familia de baja educación acumulan más recipientes que favorecen la cría de larvas Ae. aegypti, y que sería conveniente que las campañas de educación para el control del dengue se dirigieran hacia esta parte de la población

Effects of climatic and social factors on dengue incidence in Mexican municipalities in the state of Veracruz

Objective. To assess links between the social variables and longer-term El Niño-Southern Oscillation (ENSO) related weather conditions as they relate to the week-to-week changes in dengue incidence at a regional level. Materials and methods. We collected data from 10 municipalities of the Olmeca region in México, over a 10 year period (January 1995 to December 2005). Negative binomial models with distributed lags were adjusted to look for associations between changes in the weekly incidence rate of dengue fever and climate variability. Results. Our results show that it takes approximately six weeks for sea surface temperatures (SST -34) to affect dengue incidence adjusted by weather and social variables. Conclusion. Such models could be used as early as two months in advance to provide information to decision makers about potential epidemics. Elucidating the effect of climatic variability and social variables, could assist in the development of accurate early warning systems for epidemics like dengue, Chikungunya and Zika

Naturally infected Aedes aegypti

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) of the genus Flavivirus within the family Flaviviridae, originally isolated from the blood of a febrile rhesus macaque in the Ziika forest of Uganda in 1947 [1]. Although serologic evidence indicates that ZIKV has circulated in Africa and Asia for decades [2], only 14 reports of human infection were documented in the literature before 2007 [3]. Subsequently, ZIKV began causing outbreaks on islands in the Pacific before reaching the Americas in 2013 [4]. Beginning in 2015 the virus sparked widespread epidemics in the Americas, garnering international attention due to its association with severe sequelae such as Guillain–Barré syndrome in previously healthy individuals as well as Congenital Zika Syndrome in infants whose mothers were infected during pregnancy

Naturally infected Aedes aegypti collected during a Zika virus outbreak have viral titres consistent with transmission

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) of the genus Flavivirus within the family Flaviviridae, originally isolated from the blood of a febrile rhesus macaque in the Ziika forest of Uganda in 1947 [1]. Although serologic evidence indicates that ZIKV has circulated in Africa and Asia for decades [2], only 14 reports of human infection were documented in the literature before 2007 [3]. Subsequently, ZIKV began causing outbreaks on islands in the Pacific before reaching the Americas in 2013 [4]. Beginning in 2015 the virus sparked widespread epidemics in the Americas, garnering international attention due to its association with severe sequelae such as Guillain–Barré syndrome in previously healthy individuals as well as Congenital Zika Syndrome in infants whose mothers were infected during pregnancy

Climate Change Influences on Global Distributions of Dengue and Chikungunya Virus Vectors

This packet presents raster data files that accompany a manuscript submitted for publication to Philosophical Transactions of the Royal Society, titled “Climate Change Influences on Global Vector Distributions for Dengue and Chikungunya Viruses.” Included within this packet are the following data sets: • bias_layer.tif – This data layer summarizes the intensity with which Aedes mosquitoes have been sampled worldwide, according to the digital data resources that were accessed for this study. This data layer was used as a ‘bias layer’ with which to guide background sampling in the Maxent algorithm. • aegypti_present.tif – Ecological niche model for Aedes aegypti under present-day conditions. • aegypti_a1b.tif – Ecological niche model for Aedes aegypti calibrated under present-day conditions, but transferred to SRES A1B conditions for 2050 (see text for details) • aegypti_a2.tif – Ecological niche model for Aedes aegypti calibrated under present-day conditions, but transferred to SRES A2 conditions for 2050 (see text for details) • aegypti_b1.tif – Ecological niche model for Aedes aegypti calibrated under present-day conditions, but transferred to SRES B1 conditions for 2050 (see text for details) • albopictus_present.tif – Ecological niche model for Aedes albopictus under present-day conditions. • albopictus_a1b.tif – Ecological niche model for Aedes albopictus calibrated under present-day conditions, but transferred to SRES A1B conditions for 2050 (see text for details) • albopictus_a2.tif – Ecological niche model for Aedes albopictus calibrated under present-day conditions, but transferred to SRES A2 conditions for 2050 (see text for details) • albopictus_b1.tif – Ecological niche model for Aedes aegypti calibrated under present-day conditions, but transferred to SRES B1 conditions for 2050 (see text for details

Use of Unmanned Aerial Vehicles for Building a House Risk Index of Mosquito-Borne Viral Diseases

The Vector Control Program in Mexico has developed operational research strategies to identify entomological and sociodemographic parameters associated with dengue transmission in order to direct targeted actions and reduce transmission. However, these strategies have limitations in establishing their relationship with landscape analysis and dengue transmission. This study provides a proof of concept of the use of unmanned aerial vehicle technology as a possible way to collect spatial information of the landscape in real time through multispectral images for the generation of a multivariate predictive model that allows for the establishment of a risk index relating sociodemographic variables with the presence of the vector in its different larval, pupal, and adult stages. With flight times of less than 30 min, RGB orthomosaics were built, where houses, roads, highways, rivers, and trails are observed in detail, as well as in areas with a strong influence of vegetation, detailing the location of the roofs or the infrastructure of the house, grass, bushes, and trees of different dimensions, with a pixel resolution level of 5 centimeters. For the risk index, we developed a methodology based on partial least squares (PLS), which takes into account the different type of variables are involved and the geographic distribution of the houses as well. Results show the spatial pattern of downtown low-risk housing, which increases as we approach the outskirts of the town. The predictive model of dengue transmission risk developed through orthomosaics can help decision makers to plan control and public health activities