Study area and population survey
The Pirajá neighborhood (12o 53”45.00” S 38o 27’53.27” W) (Figure 1) is within a densely populated area of the major city of Salvador, Bahia, Brazil whose population is nearly 3 million (CONDER, 2016). The community borders a large city park, São Bartolomeu, that formerly protected a river and reservoir that served as a source of drinking water for the city. Population pressure surrounding the park has meant the reservoir no longer serves this purpose but is an area for recreation and some small-scale agriculture (CONDER, 2016).
According to the 2010 census, Pirajá had a population of 33,341 inhabitants of which >50% are age 20 - 49. Piped water is available to more than 95% of households and sewage is accessible to 91% (CONDER, 2016), however, many households are not connected to the system. Thirty percent earn less than one minimum monthly salary (US$213) and 40% between one and three minimum salaries (CONDER, 2016). Proximity to bodies of water and especially water development activities have been identified as a risk factor for infection with schistosomes (Clennon et al., 2004; Kabuyaya et al., 2017; Mogeni et al., 2020). Therefore, for this study, a band of homes approximately two city blocks wide that boarders the park, river, and reservoir was selected for sampling.
The study area comprised 650 households where 2,011 residents were interviewed and 1,134 provided at least one stool sample for Kato-Katz assay. Interviews and stool sampling were performed as previously described with stools collected on three different days (Blanton et al., 2015) (FigureS1). Interview data were directly entered into a REDCap database (version 9.3.1-2021 Vanderbilt University) using Android-based tablets (Android version 9.1, Samsung Galaxy Tab A 8.0).