Secular trends in child intestinal parasitic diseases in S. Paulo city, Brazil (1984-1996)

Objective Data from two consecutive household surveys undertaken in mid-80s and mid-90s allow to characterize and analyse secular trends in infant and child intestinal parasitic diseases in the city of S. Paulo, Brazil. Methods The two surveys included random population samples aged from zero to 59 months (1,016 in the period of 1984-85 and 1,280 in 1995-96). Stool samples were collected in both surveys and examined by sedimentation techniques using both unstained and Lugol-stained preparations. For each survey, the study of the social distribution of the parasitic diseases took into account tertiles of the per capita family income. For the study of the determinants of secular trends, hierarchical causal models, multivariate regression analyses and calculations analogous to the ones used to assess population attributable risks were applied. Results/Conclusions In the time span from the first to the second survey there was a substantial reduction in the prevalence of all parasites (from 30.9% to 10.7%), helminthes in general (from 22.3% to 4.8%), giardiasis (from 14.5% to 5.5%) and two ol more species of parasites (from 13.1% to 0.5%). A significant decline in prevalence was observed in all social strata and the inverse association between income and intestinal parasites was kept unchanged in the period. Positive changes in distal (family income and maternal schooling) and intermediate determinants (housing, sanitation, and access to health care) of helminthic disease could substantially explain part of its decline in the period. The decline in giardiasis was attributed to improvement in maternal schooling, housing and sanitation. The duplication in the attendance rate to day care nurseries may have restricted the decline I rate in the giardiasis prevalence ill the study period.