Mosquitoes that breed in urban landscapes, largely using man-made containers, are of considerable pestiferous and medical significance. Studies have shown that container type, as well as abundance, size and location are important determinants of juvenile survival and our work has demonstrated that differences in the abundance and quality of container habitat across neighborhoods result in inequitable resident exposure. Although residents in lower income neighborhoods (which tend to have greater rates of infrastructure abandonment) are at greater risk of mosquito exposure for most of the season, resident actions and infrastructure on higher-income blocks (which also have few or no abandoned buildings) can effectively decouple mosquito population growth from environmental regulation due to high temperatures and drought. Likewise, the abundance of host-seeking adult mosquitoes on a city block is positively associated with the density of local container habitat. Thus, we expect that removing juvenile mosquito habitat should lead to reduced adult abundance but with potentially different overall impact on mosquito populations across neighborhoods. We describe a rigorous experimental intervention that removed accessible juvenile mosquito habitat from entire city blocks across two neighborhoods representing a gradient of social and ecological conditions in Baltimore MD.
Our habitat removal intervention had counterintuitive results, with greater numbers of adult Aedes albopictus on treatment blocks post-intervention and more positive growth rates on treatment versus control blocks. We found no significant effect on Culex populations. Unlike Culex mosquitoes that can disperse 1-2 km, Ae. albopictus are likely to host-seek less than 100 meters from where they emerge and females lay eggs across surfaces of multiple container habitats. We conclude that removing accessible containers may have re-focused oviposition on higher quality habitat not readily observed or treated by residents, such as underground or roof-level sources. In the wake of recent arboviral emergence in recent years, communities across the globe are encouraged to reduce availability of breeding containers. Yet the ecological mechanisms and conditions supporting persistence of mosquito populations are not understood well enough to predict where source reduction is most effective and where it might have less desirable outcomes.