Prevalence and distribution of soil-transmitted helminth (STH) infections in urban and indigenous schoolchildren in Ortigueira, State of Paranà, Brasil: implications for control.

Soil-transmitted helminth (STH) infections represent a major public health problem in poor and developing countries. During the period September-October 1998 we conducted an epidemiological survey of STH infections in schoolchildren of an urban area (group A) and an indigenous reserve (group B), in the Municipality of Ortigueira, State of Paranà, Brazil, to assess potential benefits of mass treatment. Stool samples were examined for helminth eggs by quantitative (Kato-Katz) technique to determine the prevalence and intensity of intestinal parasitic infection. Moreover, we examined the relationship between prevalence and intensity of STH infections and housing/hygienic factors (by means of a 7-item questionnaire). 236 schoolchildren aged 5-15 years were enrolled, 136 in group A and 100 in group B. The prevalence of STH infections was significantly higher in group B (93%) than in group A (22%) (P < 0.001). Detected parasites were: A. lumbricoides (16.1% prevalence in group A, 88% in group B, P < 0.001), hookworms (5.8% in group A, 52% in group B, P < 0.001) and T. trichiura (5.1% in group A, 2% in group B, P = 0.2). Heavy infections were detected in 2.9% and 23% of the children in group A and B, respectively (P < 0.001). Housing/hygienic indicators were significantly poorer in group B. A statistically significant correlation was observed between total prevalence of STH infections and prevalence of high-intensity infections with most housing/hygienic variables. On the basis of these results, mass treatment and educational interventions were suggested for the indigenous community, whereas target treatment and educational interventions were suggested for the urban community. Even in a geographically homogeneous area different epidemiological realities can be found, which in turn can influence infection levels and control programmes.