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. 2014 Oct 2;8(10):e3186.
doi: 10.1371/journal.pntd.0003186. eCollection 2014 Oct.

Sources and distribution of surface water fecal contamination and prevalence of schistosomiasis in a Brazilian village

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Sources and distribution of surface water fecal contamination and prevalence of schistosomiasis in a Brazilian village

Rafael Ponce-Terashima et al. PLoS Negl Trop Dis. .

Abstract

Background: The relationship between poor sanitation and the parasitic infection schistosomiasis is well-known, but still rarely investigated directly and quantitatively. In a Brazilian village we correlated the spatial concentration of human fecal contamination of its main river and the prevalence of schistosomiasis.

Methods: We validated three bacterial markers of contamination in this population by high throughput sequencing of the 16S rRNA gene and qPCR of feces from local residents. The qPCR of genetic markers from the 16S rRNA gene of Bacteroides-Prevotella group, Bacteroides HF8 cluster, and Lachnospiraceae Lachno2 cluster as well as sequencing was performed on georeferenced samples of river water. Ninety-six percent of residents were examined for schistosomiasis.

Findings: Sequence of 16S rRNA DNA from stool samples validated the relative human specificity of the HF8 and Lachno 2 fecal indicators compared to animals. The concentration of fecal contamination increased markedly along the river as it passed an increasing proportion of the population on its way downstream as did the sequence reads from bacterial families associated with human feces. Lachnospiraceae provided the most robust signal of human fecal contamination. The prevalence of schistosomiasis likewise increased downstream. Using a linear regression model, a significant correlation was demonstrated between the prevalence of S. mansoni infection and local concentration of human fecal contamination based on the Lachnospiraceae Lachno2 cluster (r2 0.53) as compared to the correlation with the general fecal marker E. coli (r2 0.28).

Interpretation: Fecal contamination in rivers has a downstream cumulative effect. The transmission of schistosomiasis correlates with very local factors probably resulting from the distribution of human fecal contamination, the limited movement of snails, and the frequency of water contact near the home. In endemic regions, the combined use of human associated bacterial markers and GIS analysis can quantitatively identify areas with risk for schistosomiasis as well as assess the efficacy of sanitation and environmental interventions for prevention.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. (a) Study area: village of Jenipapo in the state of Bahia, Brazil.
(b) Kernel density distribution of human population. (c) Kernel density distribution of sewage draining directly into the river. (d) Kernel density distribution of S. mansoni infection.
Figure 2
Figure 2. Distribution of bacterial concentration along the Jiquiriçá River.
qPCR measurement of target DNA from anaerobic bacterial families and E. coli in water samples collected along the length of the river in Jenipapo, Bahia, Brazil. S1–S8 primary sites of human water contact. Distances along the river are provided in meters. Bacteroides and Prevotella - general, Lachno2 - human-indicative Lachnospiraceae gene cluster, HF8 - human-indicative Bacteroidales gene cluster, BacR - ruminant-indicative Bacteroidales gene cluster.
Figure 3
Figure 3. Distribution of E. coli and coliform concentration by bacterial culture along the Jiquiriçá River.
S1–S8 primary sites of human water contact. Distances along the river are provided in meters. CFU - colony forming units. No sample was collected for site 1.
Figure 4
Figure 4. River microbial communities (Family level).
River samples were collected from five points along the Jiquiriçá River in Jenipapo, Brazil on August 18, 2012. Microbial community populations of five river samples. The V6 hypervariable regions of the 16S rRNA gene from community genomic DNA were amplified and sequenced using Hi-Seq Illumina Sequencing. Taxonomy was assigned to sequences using GAST and taxonomic counts were normalized to the maximum number of sequences. Only the most abundant genera (>1% of at least one sample) are presented. Families discussed in the text are outlined.
Figure 5
Figure 5. Map of Jenipapo with the area of houses divided in a 200 m2 grid.
Schistosomiasis prevalence for each 200 m2 block was estimated. Infection prevalence increased downstream.

References

    1. Savichtcheva O, Okabe S (2006) Alternative indicators of fecal pollution: relations with pathogens and conventional indicators, current methodologies for direct pathogen monitoring and future application perspectives. Water Res 40: 2463–2476. - PubMed
    1. USEPA (2012) US Environmental Protection Agency: 2012 Recreational Water Quality Criteria. 20-F-12-058.
    1. Wade TJ, Pai N, Eisenberg JN, Colford JM Jr (2003) Do U.S. Environmental Protection Agency water quality guidelines for recreational waters prevent gastrointestinal illness? A systematic review and meta-analysis. Environ Health Perspect 111: 1102–1109. - PMC - PubMed
    1. Wu J, Long SC, Das D, Dorner SM (2011) Are microbial indicators and pathogens correlated? A statistical analysis of 40 years of research. J Water Health 9: 265–278. - PubMed
    1. McFeters GA, Bissonnette GK, Jezeski JJ, Thomson CA, Stuart DG (1974) Comparative survival of indicator bacteria and enteric pathogens in well water. Appl Microbiol 27: 823–829. - PMC - PubMed

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