Aedes aegypti abundance in urban neighborhoods of Maricopa County, Arizona, is linked to increasing socioeconomic status and tree cover

Abstract

Background: Understanding coupled human-environment factors which promote Aedes aegypti abundance is critical to preventing the spread of Zika, chikungunya, yellow fever and dengue viruses. High temperatures and aridity theoretically make arid lands inhospitable for Ae. aegypti mosquitoes, yet their populations are well established in many desert cities.

Methods: We investigated associations between socioeconomic and built environment factors and Ae. aegypti abundance in Maricopa County, Arizona, home to Phoenix metropolitan area. Maricopa County Environmental Services conducts weekly mosquito surveillance with CO₂-baited Encephalitis Vector Survey or BG-Sentinel traps at > 850 locations throughout the county. Counts of adult female Ae. aegypti from 2014 to 2017 were joined with US Census data, precipitation and temperature data, and 2015 land cover from high-resolution (1 m) aerial images from the National Agricultural Imagery Program.

Results: From 139,729 trap-nights, 107,116 Ae. aegypti females were captured. Counts were significantly positively associated with higher socioeconomic status. This association was partially explained by higher densities of non-native landscaping in wealthier neighborhoods; a 1% increase in the density of tree cover around the trap was associated with a ~ 7% higher count of Ae. aegypti (95% CI: 6-9%).

Conclusions: Many models predict that climate change will drive aridification in some heavily populated regions, including those where Ae. aegypti are widespread. City climate change adaptation plans often include green spaces and vegetation cover to increase resilience to extreme heat, but these may unintentionally create hospitable microclimates for Ae. aegypti. This possible outcome should be addressed to reduce the potential for outbreaks of Aedes-borne diseases in desert cities.

Keywords: Aedes aegypti; Coupled human-natural systems; Desert; Land cover; Microclimate.

Fig. 1

Counts of adult female Ae. aegypti mosquitoes captured per trap-night by month, Maricopa County, Arizona, 2014–2017. Intervals for trap counts were manually defined for consistency across months and because of the extremely right skewed nature of the data

Fig. 2

Locations of mosquito traps and average count per trap night during rainy season months (July–October), Maricopa County, 2014–2017

Fig. 3

Counts of Aedes aegypti females per trap-night by month and quartile of tree cover within 50 m of the trap (Q4 = highest), Maricopa County, 2014–2017. Intervals for trap counts were manually defined for consistency across months and because of the extremely right skewed nature of the data

Fig. 4

Counts of Aedes aegypti females per trap-night by month and quartile of grass cover (Q4 = highest), Maricopa County, 2014–2017. Intervals for trap counts were manually defined for consistency across months and because of the extremely right skewed nature of the data

Fig. 5

Counts of Aedes aegypti females per trap-night by month and quartile of poverty (Q4 = most poverty), Maricopa County, 2014–2017. Intervals for trap counts were manually defined for consistency across months and because of the extremely right skewed nature of the data