Comparison of self-reported and observed water contact measures in Schistosoma japonicum-endemic villages in Leyte, The Philippines

Background We compared individuals' self-reported water contact from a questionnaire to direct observation of water contact. Questionnaires that accurately capture water contact are necessary to risk-stratify individuals and communities at high risk for schistosomiasis. Methods Individuals (N=677) ages 7-30 y were included from three Schistosoma japonicum-endemic villages in Leyte, The Philippines. Each individual was observed for 12 d over the course of the 18-month study and the questionnaire was administered six times. A questionnaire index was derived that captured the number of self-reported contacts with water bodies for any purpose. An exposure index was created based on the sum of contacts that was weighted by the percentage of body surface area (BSA) exposed and exposure duration. Results Of 16 water contact activities, only bathing and washing clothes exhibited a significant, positive correlation between self-reported contacts and the observed exposure index related to those contacts. Conclusions We found that only the reported frequencies of bathing and washing clothes were significantly related to an individual's overall observed exposure index, while use of all reported contacts was not related to the observed exposure. This study further supports the need for questionnaires to be augmented by some measure of how much BSA is exposed and/or time is spent in the water on average for a specific activity.