<p>The history of Schistosomiasis in China remains unexplained due to insufficient historical documentation of the host parasite relationship. However, both earlier studies and oral materials from the 1950s indicate historical variation in the disease’s severity. This article explores an innovative approach for examining this hidden history. In particular, the author utilizes genealogical and other documents of the Chen family. Its size and the inferred Schistosomiasis induced anomalous depopulation of the clan can be observed in genealogies in the southern Dongting Lake region. To trace the disease’s sources and effects, the article adopts an ecosystem viewpoint. It explores the role of the parasite and the snail, which served as the principal transmission agent, to shed light on how human environmental transformations and interventions created a beneficial <i>umwelt</i> of the pathogen. Combined with historical hydrological and water conservancy construction records, this article finds that the disease severity observed since the 1950s was the outcome of longue duréée human-environment interaction and that no significant impact of Schistosomiasis occurred prior to the late-eighteenth century. Furthermore, the sequence of pathogen habitat migration patterns and their causes should be illuminated to better understand the terrain shift, from the south to the north that is occurring today.</p>