Based on dissertation research from the Fatick region of Senegal, this paper illustrates relationships between local knowledge and development science. Following literature suggesting African parallels to biological concepts in public health, I suggest that there are also parallels for understandings of how scientific knowledge is created, disseminated, and used. Discussions with local patients, health personnel, and healers suggest that while some public health projects achieve their aims, many fall short, often because goals are framed in epidemiologic terms of great importance to administrators of the public health system but of relatively little concern to local populations, thus prompting little involvement. However, some people have welcomed projects because of a perception that those involved can immediately benefit through connections to networks of personal relations, scientific expertise, and material resources. People in Fatick have therefore encouraged development actors to engage with and belong to their communities. Such acceptance has numerous historical precedents and allows many “guests” the privilege of moving in and out of communities while still maintaining ties and status. Local interpretations and strategies related to the spatiality of health development are linked to other understandings of healing knowledge, which can be both socially “grown” around Fatick and materially “extended” elsewhere. Many locals place an intentional lack of balance between these two aspects at the heart of certain failures in health and development science. Their interpretive strategies thereby reframe public health efforts in important ways that could potentially make health development efforts more relevant to people’s concerns in Fatick and elsewhere.