Household-level risk factors for Aedes aegypti pupal density in Guayaquil, Ecuador

Thien-An Ha,Patricio Ponce,John M Marshall,Varsovia Cevallos,Karina Lalangui,Tomás M León

doi:10.1186/s13071-021-04913-0

Abstract

BackgroundVector-borne diseases are a major cause of disease burden in Guayaquil, Ecuador, especially arboviruses spread by Aedes aegypti mosquitoes. Understanding which household characteristics and risk factors lead to higher Ae. aegypti densities and consequent disease risk can help inform and optimize vector control programs.MethodsCross-sectional entomological surveys were conducted in Guayaquil between 2013 and 2016, covering household demographics, municipal services, potential breeding containers, presence of Ae. aegypti larvae and pupae, and history of using mosquito control methods. A zero-truncated negative binomial regression model was fitted to data for estimating the household pupal index. An additional model assessed the factors of the most productive breeding sites across all of the households.ResultsOf surveyed households, 610 satisfied inclusion criteria. The final household-level model found that collection of large solid items (e.g., furniture and tires) and rainfall the week of and 2 weeks before collection were negatively correlated with average pupae per container, while bed canopy use, unemployment, container water volume, and the interaction between large solid collection and rainfall 2 weeks before the sampling event were positively correlated. Selection of these variables across other top candidate models with ∆AICc < 1 was robust, with the strongest effects from large solid collection and bed canopy use. The final container-level model explaining the characteristics of breeding sites found that contaminated water is positively correlated with Ae. aegypti pupae counts while breeding sites composed of car parts, furniture, sewerage parts, vases, were all negatively correlated.ConclusionsHaving access to municipal services like bulky item pickup was effective at reducing mosquito proliferation in households. Association of bed canopy use with higher mosquito densities is unexpected, and may be a consequence of large local mosquito populations or due to limited use or effectiveness of other vector control methods. The impact of rainfall on mosquito density is multifaceted, as it may both create new habitat and “wash out” existing habitat. Providing services and social/technical interventions focused on monitoring and eliminating productive breeding sites is important for reducing aquatic-stage mosquito densities in households at risk for Ae. aegypti-transmitted diseases.Graphical

Highlights

Vector-borne diseases are a major cause of disease burden in Guayaquil, Ecuador, especially arbovi‐ ruses spread by Aedes aegypti mosquitoes
We used the Akaike information criterion corrected for small sample sizes (AICc) to compare all the candidate models (Additional file 5: Fig S1 for the household-level models and Fig S2 for the container-level model)
The findings of this study provide evidence that Ae. aegypti proliferation is influenced by specific household risk factors

Summary

Introduction

Vector-borne diseases are a major cause of disease burden in Guayaquil, Ecuador, especially arbovi‐ ruses spread by Aedes aegypti mosquitoes. Understanding which household characteristics and risk factors lead to higher Ae. aegypti densities and consequent disease risk can help inform and optimize vector control programs. Vector-borne febrile illnesses such as dengue, chikungunya, and Zika virus are of pressing public health concern in Latin America and the Caribbean [1]. The mosquito Aedes aegypti is the region’s primary vector of these arboviruses, which co-circulate in populations in the tropics and subtropics [1, 2]. In Ecuador, each household currently employs, on average, five different mosquito control methods, including sprays, aerosols, repellents, mosquito coils, screens, and bed nets [1]

Methods

Results

Discussion

Conclusion