Assessing physical and environmental predictors of bovine Schistosoma japonicum infection in rural China

Background Bovines have been repeatedly highlighted as a major reservoir for human Schistosoma japonicum infection in rural farming villages in China. However, little is known about the individual and environmental risk factors for bovine schistosomiasis infection. The current body of literature on individual-level risk factors features inconsistent, and sometimes contradictory results, and to date, few studies have assessed the broader environmental conditions that predict bovine schistosomiasis. Methodology/Principal Findings Using data collected as a part of a longitudinal study in 39 rural villages in Sichuan, China from 2007 to 2016, we aimed to identifying the strongest individual, household and village-level predictors of bovine S. japonicum infection. Candidate predictors for this assessment included: 1) physical/biological characteristics of bovines, 2) potential human sources of environmental schistosomes, 3) socio-economic indicators, 4) potential animal reservoirs, and 5) agricultural risk factors. A Random Forests machine learning approach was used to determine which of our candidate predictors serve as the best predictors of bovine schistosomiasis infection in each survey year. Of the five categories of predictors, high-risk agricultural practices and animal reservoirs, specifically, bovine density at the village-level, were repeatedly found to be among the top predictors of bovine S. japonicum infection. Conclusion/Significance Our findings highlight the potential utility of presumptively treating bovines residing in villages and households that engage in high-risk agricultural practices, or bovines belonging to villages with particularly high levels of bovine ownership. Additionally, village-level predictors were stronger predictors of bovine infection than household-level predictors, suggesting future investigations and interventions may need to apply a broad ecological lens in order to successfully extricate and address environmental sources of ongoing transmission.