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).