Field projects

Climate change will have large and potentially surprising effects on a wide range of biological and social systems. One important consequence of climate change is likely to be alterations in the geographic range, extent, and severity of many infectious diseases. Human adaptive responses to changing environments are often strongly nonlinear, as is pathogen transmission. The coupling of these two nonlinear processes suggests that even small changes in people’s livelihood behavior could have cascading effects on infectious disease dynamics. I have two field-based projects in Namibia that explore these dynamics in two very different socio-ecological contexts.

Environmental drivers of endemic gonorrhea among semi-nomadic pastoralists: Kaokoveld, Namibia

We are exploring how ecological adaptation to intense drought is affecting Neisseria gonorrhoeae (gonorrhea) epidemiology among the Himba pastoralists of Kaokoveld (northwest) Namibia. Specifically, we aim to test the hypothesis that drought alters the ecology of transmission cycles, leaving traces of environmental forcing even in a directly-transmitted pathogen like gonorrhea. Gonorrhea is highly prevalent across Kaokoveld because maintaining multiple concurrent sexual partners is culturally acceptable and, I argue, ecologically valuable. Meanwhile, gonorrhea incidence and persistence varies temporally according subsistence dispersal patterns and seasonal shifts in structure of sexual networks. Although well-adapted to arid living, the Kaokoveld pastoralists are experiencing the worst known drought in history. Surviving drought has forced people to alter their subsistence and mobility strategies, which, in turn, has affected the frequency and timing of access to sexual partners. Climate change portends longer and more severe droughts and the responses that we currently observe may provide insights into people’s long-term social and ecological coping strategies and to how changes in human-environmental systems alter the selective landscape of directly transmitted pathogens.

Mixed subsistence, food security, and tuberculosis among the Ju|’hoansi San: Tsumkwe, Namibia

The Ju|’Hoansi San can trace their residency in the Kalahari back for tens of thousands of years, living exclusively as highly mobile hunter-gathers. In recent generations, Ju|’hoansi communities have adopted a mixed subsistence strategy that is still variously reliant on foraging and hunting. Modern village life is much more sedentary than in the past and everyone is strongly connected to small urban settlements, for work, healthcare, remittances, and education. While village-living Ju|’hoan households frequently employ a wide range subsistence practices, including gathering, hunting, gardening, animal husbandry, and informal wage labor, each of these strategies is vulnerable to environmental variation and scarcity. Meanwhile, tuberculosis, especially drug-resistant strains, has long been a major health problem in San communities, but little is known about local transmission dynamics or the ecological vulnerabilities to exposure. In this new and developing project, we are exploring how intra- and inter-household patterns of subsistence and food insecurity influence vulnerability to active TB infection and exposure.