[Evolution of the prevalence of intestinal parasitosis among schoolchildren in Caxias do Sul, RS].

Reports on the prevalence of intestinal parasitosis in Brazil have been local in nature, with descriptions of different populations, which makes comprehensive diagnosis difficult. With the aim of studying the variation in the prevalence of intestinal parasitosis among schoolchildren in Caxias do Sul, Rio Grande do Sul, over a 35-year period, 9,787 parasitological stool tests that had been performed using centrifugal sedimentation were evaluated. There were positive results from 5,655 samples (58%), and the most prevalent infestations were of Ascaris lumbricoides (47%), Trichuris trichiura (36%), Enterobius vermicularis (8%) and the protozoa Giardia lamblia (24%) and Entamoeba coli (20%). The overall prevalence diminished from 89% to 37%, indicating an average decrease of 1.4% per year. Reductions in prevalence were observed for Ascaris lumbricoides (61 to 26%) and Trichuris trichiura (38 to 18%). No significant change was observed for Giardia lamblia. The prevalence of Entamoeba coli increased from 29 to 46%. The decreases in helminth prevalence were probably due to infrastructure improvements and educational actions undertaken in schools.