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. 2010 Nov;118(11):1637-42.
doi: 10.1289/ehp.1002058.

Impact of a citywide sanitation program in Northeast Brazil on intestinal parasites infection in young children

Mauricio L Barreto  1 , Bernd Genser, Agostino Strina, Maria Gloria Teixeira, Ana Marlucia O Assis, Rita F Rego, Carlos A Teles, Matildes S Prado, Sheila Matos, Neuza M Alcântara-Neves, Sandy Cairncross
Affiliations

Impact of a citywide sanitation program in Northeast Brazil on intestinal parasites infection in young children

Mauricio L Barreto et al. Environ Health Perspect. 2010 Nov.

Abstract

Background: Sanitation affects health, especially that of young children. Residents of Salvador, in Northeast Brazil, have had a high prevalence of intestinal parasites. A citywide sanitation intervention started in 1996 aimed to raise the level of sewer coverage from 26% to 80% of households.

Objectives: We evaluated the impact of this intervention on the prevalence of Ascaris lumbricoides, Trichuris trichuria, and Giardia duodenalis infections in preschool children.

Methods: The evaluation was composed of two cross-sectional studies (1998 and 2003-2004), each of a sample of 681 and 976 children 1-4 years of age, respectively. Children were sampled from 24 sentinel areas chosen to represent the range of environmental conditions in the study site. Data were collected using an individual/household questionnaire, and an environmental survey was conducted in each area before and after the intervention to assess basic household and neighborhood sanitation conditions. Stool samples were examined for the presence of intestinal parasites. The effect of the intervention was estimated by hierarchical modeling, fitting a sequence of multivariate regression models.

Findings: The prevalence ofA. lumbricoides infection was reduced from 24.4% to 12.0%, T. trichuria from 18.0% to 5.0%, and G. duodenalis from 14.1% to 5.3%. Most of this reduction appeared to be explained by the increased coverage in each neighborhood by the sewage system constructed during the intervention. The key explanatory variable was thus an ecological measure of exposure and not household-based, suggesting that the parasite transmission prevented by the program was mainly in the public (vs. the domestic) domain.

Conclusion: This study, using advanced statistical modeling to control for individual and ecological potential confounders, demonstrates the impact on intestinal parasites of sanitation improvements implemented at the scale of a large population.

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Figures

Figure 1
Figure 1
Conceptual model to evaluate the effect of the Bahia Azul sanitation program.
Figure 2
Figure 2
Proportion of households connected to Bahia Azul program sewers in 2004 and baseline (1998) prevalence of (A) A. lumbricoides, (B) T. trichiura, and (C) G. duodenalis by sentinel area; 1,657 children 0–4 years of age, Salvador, Brazil. Each point represents the estimate for a sentinel area, and its size reflects the number of households in that area. The line on each graph is fitted by bivariate linear regression, weighted by the number of households in each sentinel area.
Figure 3
Figure 3
PR of infection with (A) A. lumbricoides, (B) T. trichiura, and (C) G. duodenalis (after vs. before the intervention) plotted against baseline prevalence of the respective parasite in each sentinel area; 1,657 children 0–4 years of age, in Salvador, Brazil, 1997–1998 and 2003–2004. PRs are adjusted for age and sex. Each point represents the estimate for a sentinel area, and its size reflects the number of households in that area. The line on each graph is fitted by bivariate linear regression, weighted by the number of households in each sentinel area.
See this image and copyright information in PMC

References

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