Socio-environmental assessment of Aedes aegypti distribution and risk of chikungunya in vulnerable community.

Abstract

Chikungunya virus (CHIKV), transmitted by Aedes mosquitoes, poses a major public health challenge in tropical regions. In Brazil, its incidence has increased, especially in socioeconomically vulnerable areas, where environmental conditions favor the proliferation of vectors. Our objective was to assess the socioeconomic and environmental vulnerabilities associated with the spatial distribution of a) Ae. aegypti and b) resident exposure to CHIKV in a low-income community. Identifying key exposure hotspots, our work improves our understanding of CHIKV transmission in informal settlements and facilitates community-based interventions to mitigate CHIKV risk. We monitored Ae. aegypti using ovitraps and conducted a serological survey from October 2021 to June 2022 in a vulnerable informal community in Salvador, Brazil. Blood samples and sociodemographic, household, and environmental data were collected from residents aged ≥5 years. CHIKV serology was performed, and spatial models using Integrated Nested Laplace Approximation assessed vector distribution, seropositivity, and associated factors. Among 194 ovitraps, posterior estimates indicated higher egg counts in peridomicile locations (IRR = 1  .99; CrI:1.3 1-3.0 6); households experiencing food insecurity (IRR = 1.77; CrI: 1.05 - 2.99), properties with unpaved yards (IRR = 3.76; CrI:2.31 -6.18), and areas with greater garbage density (IRR = 1.25; CrI:1.01 -1.56). Among 888 participants, Bayesian spatial modeling identified factors associated with CHIKV seropositivity: elderly (OR= 2.24; CrI:1.16-4.35), uncovered brick walls (OR=2.29; CrI:1.16-4.55), the presence of yards, either paved (OR=2.06; CrI:1.30-3.00) or unpaved (OR=2.71; CrI:1.73-4.25), and self-reported mosquito sightings (OR=1.94; CrI:1.19-3.18). In addition, remotely sensed Land Surface Temperature (OR=1.33; CrI:0.98-1.83) and the spatial ovitraps egg counts (OR=1.14; CrI:0.87-1.52) were relevant variables. Our high-resolution study identified fine-scale vulnerabilities linked to both Ae. aegypti abundance and heightened risk of CHIKV transmission. Based on our findings, effective control strategies should not only focus on traditional methods such as enhancing basic urban infrastructure and services and promoting community awareness, but also target specific breeding sites around homes, address garbage accumulation, and consider the influence of micro-scale temperature variations. These results emphasize the importance of tailored, neighborhood-specific interventions to effectively reduce chikungunya transmission in high-risk communities.