Climate, Ecology, and the Socio-Political Dimensions of Mosquito-Borne Disease in the Southern United States

Abstract

Infectious organisms, such as dengue and West Nile viruses, are understood to be part of complex ecologies. The same is true for their common vectors, Aedes and Culex mosquitoes. Standing water, whether from human or naturally fed sources, provides the necessary breeding habitat for immature stages. Climatic variables such as temperature and rainfall can both directly impact the amount of water available for breeding. Temperature can alter this amount via evaporation, while precipitation can maintain or refill breeding sites. The effects of temperature also partially govern the lifecycle and development of these vectors and viruses. Human action and management can further mitigate these sites by eliminating them through dumping standing water or adding insecticide, or conversely promoting them. These factors can impact the spatial distribution of these organisms at multiple scales, such as global patterns of disease, as well as patterns of risk within urban areas. This dissertation examines the ecology of two mosquito-borne diseases, dengue fever and West Nile fever, at multiple scales and asks, 1. How do environmental changes shift distributions of mosquito-borne diseases? and 2. How do local actors and residents understand, respond to, and manage these emerging infections? Dengue fever is one of the most important and fastest spreading global vector-borne diseases. At a large spatio-temporal scale, potential and future dengue transmission is assessed under current and future (2045-65) climate change scenarios across the southern US. Understanding the differential impacts of climate on the Ae. aegypti mosquito and dengue virus is essential for projecting the shifting geographies of dengue fever. This includes considering both temperature and precipitation impacts. The results suggest that winter temperatures may be limiting dengue transmission in the southern US currently, but this may change under climate change. This is particularly true for the Gulf Coast region, which becomes more climatically suitable for dengue transmission under future analysis. To understand the variance of disease risk within urban spaces, the same dynamic mosquito model was coupled with remotely sensed imagery and parameterized for Culex quinquefasciatus mosquitoes to visualize mosquito risks across the city of Tucson. Despite an arid climate, West Nile virus is an ongoing public health concern in Arizona. The maps, visualized at multiple scales, were used to assess individual perceptions of mosquito abundance and control responsibility held by residents and health officials. The results show disparate interpretations of mosquito risk among these groups, with differing calls for responsibility and action. This further shows the ways in which maps of environmental and health hazards are not only reflective of certain landscapes, but also productive. From a public health perspective, this paper is useful for understanding shifting perceptions of disease landscapes and how they match with ecological realities. While maps and modeling techniques are useful for assessing risk over various scales, the spaces of interaction between disease vectors and humans is particularly local. These interactions, and the creation or eradication of breeding habitats, are always a simultaneous relationship between environmental factors and human action. This is particularly true for the dengue fever vector, Ae. aegypti, which lives in close proximity to humans. Grounded by fieldwork conducted in Key West, FL, the site of two years of dengue fever outbreaks in 2009 and 2010, the final component of this dissertation examines how residents in Key West understand mosquito control responsibility, and what complicates the effective control of the vector on the island. While it was found that residents are highly active in monitoring and controlling mosquitoes in and around their yards, important socio-ecological factors are identified that stand to complicate control efforts. The decisions people make about their risks and around their homes as they manage the ecological spaces of the mosquito are crucial for effective public health practice.