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


OBJECTIVE
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.


RESULTS
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.


CONCLUSIONS
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.
Barreto
Mauricio L
ML
Instituto de Saúde Coletiva, Federal University of Bahia, Salvador, Brazil. mauricio@ufba.br
Genser
Bernd
B
Strina
Agostino
A
Teixeira
Maria Gloria
MG
Assis
Ana Marlucia O
AM
Rego
Rita F
RF
Teles
Carlos A
CA
Prado
Matildes S
MS
Matos
Sheila
S
Alcântara-Neves
Neuza M
NM
Cairncross
Sandy
S
D000818:Animals; D001196:Ascariasis / Q000453:epidemiology / Q000517:prevention & control; D017164:Ascaris lumbricoides / Q000302:isolation & purification; D001938:Brazil; D002675:Child, Preschool; D002947:Cities; D003140:Communicable Disease Control / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D005618:Fresh Water / Q000469:parasitology; D005872:Giardia / Q000302:isolation & purification; D005873:Giardiasis / Q000453:epidemiology / Q000517:prevention & control; D006801:Humans; D007223:Infant; D008297:Male; D010272:Parasitic Diseases / Q000453:epidemiology* / Q000517:prevention & control; D012499:Sanitation / Q000379:methods*; D012722:Sewage / Q000469:parasitology; D014257:Trichuriasis / Q000453:epidemiology / Q000517:prevention & control; D014258:Trichuris / Q000302:isolation & purification
D012722:Sewage