Determinants of arbovirus vector density as a measure of transmission risk in regions of recent Zika virus introduction in the Americas

Abstract

Background The global impact of Zika virus in Latin America and the Caribbean has drawn renewed attention to circulating mosquito-borne viruses in this region, such as dengue and chikungunya. Our objective was to assess socio-ecological factors associated with Aedes mosquito vector density as a measure of arboviral transmission risk in three cities of potential recent Zika virus introduction: Ibagué, Colombia; Manta, Ecuador; and Posadas, Argentina, in order to inform disease mitigation strategies. Methods We monitored Aedes mosquito populations over 12 months starting in 2018 in a total of 1,086 randomly selected households, using indoor and peridomestic mosquito collection methods. For each sampled household, we collected socio-economic data using structured questionnaires and data on microenvironmental conditions using iButton data loggers. Results A total of 3,230 female Aedes mosquitoes were collected, of which 99.8% were Ae. aegypti and 0.2% were Ae. albopictus. Mean female Aedes spp. mosquito abundance per household was 1.71. We modeled the interaction between neighborhood and household wealth profiles, and found significantly lower Aedes density in highest compared to lowest and middle wealth households, although the effect differed by level of neighborhood wealth. We used mixed-effects Poisson regression analyses to identify predictors of Aedes density, using month, neighborhood, and country as random-effect variables. Across study sites, the number of household occupants (Incidence rate ratio, IRR = 1.08), presence of entry points for mosquitoes into the household (IRR = 1.51), and presence of decorative vegetation (IRR = 1.52) were associated with higher Aedes density; while being in the highest wealth tertile of household wealth (IRR = 0.78), knowledge of how arboviruses are transmitted (IRR = 0.94) and regular emptying of water containers by occupants (IRR = 0.79) were associated with lower Aedes density. Conclusions Our study addresses the complexities of arbovirus vectors of global significance at the interface between society and the environment. Our results point to several determinants of Aedes mosquito vector density in countries with co-circulation of multiple Aedes-borne viruses, and could help us identify targets of practical intervention for disease prevention and control.