Exposure to Schistosoma mansoni infection in a rural area in Brazil. II: Household risk factors

A number of studies have pointed out the potential importance of the househ old in the transmission of schistosomiasis. The clustering of domestic acti vities associated with water collection, storage, and usage can result in t he sharing of transmission sites and infective water contact behaviours. In this study, we employed a variance component method to estimate effects du e to individual risk factors and shared residence on the variance in faecal egg counts during Schistosoma mansoni infection. A suite of covariates, wh ich included demographic, socioeconomic, water supply, and water contact be haviour terms, contributed 15% to the variance in faecal egg counts. Shared residence alone accounted for 28% of the variance in faecal egg excretion. When both the suite of covariates and shared residence were considered in the same model, shared residence still contributed 22% to the variance in i nfection intensity. These results point to the importance of shared residen ce as a means of capturing the complex interrelationship between shared dem ographic, socioeconomic, physical environmental, and behavioural factors th at influence transmission of schistosomiasis at the household level.