Effect of Sewerage on the Contamination of Soil with PathogenicLeptospirain Urban Slums

Leptospirosis is an environmentally transmitted zoonotic disease caused by pathogenicLeptospiraspp. that affects poor communities worldwide. In urban slums, leptospirosis is associated with deficient sanitary infrastructure. Yet, the role of sewerage in the reduction of the environmental contamination with pathogenicLeptospirahas not been explored. Here, we conducted a survey of the pathogen in soils surrounding open and closed sewer sections in six urban slums in Brazil. We found that soils surrounding conventionally closed sewers (governmental interventions) were 3 times less likely to contain pathogenicLeptospira(inverse OR 3.44, 95% CI = 1.66-8.33;p< 0.001) and contained a 6 times lower load of the pathogen (0.82 log10units difference,p< 0.01) when compared to their open counterparts. However, no differences were observed in community-closed sewers (poor-quality closings performed by the slum dwellers). Human fecal markers (BacHum) were positively associated with pathogenicLeptospiraeven in closed sewers, and rat presence was not predictive of the presence of the pathogen in soils, suggesting that site-specific rodent control may not be sufficient to reduce the environmental contamination withLeptospira. Overall, our results indicate that sewerage expansion to urban slums may help reduce the environmental contamination with the pathogen and therefore reduce the risk of human leptospirosis.