Household epidemiology of Entamoeba histolytica infection in an urban community in northeastern Brazil

The natural history of infection,vith Entamoeba histolytica was studied in 2 slum communities in northeastern Brazil. Twenty-eight index patients colo nized with E. histolytica were identified. Three stool specimens from the i ndex patients and their household contacts were gathered over a 45-day peri od and tested for E. histolytica by means of a specific enzyme-linked immun osorbent assay-ba-sed detection kit. The detection kit is an antigen captur e assay that has been shown to be highly specific for E. histolytica and do es not detect nonpathogenic Entamoeba dispar or other enteric organisms. Bl ood samples were also collected at the start of the study, at 45 days, and at 6 months and analyzed for E. histolytica-specific antibody. High rates o f colonization were seen in the family units. Colonization was self-limited , with 85% of colonized patients clearing their infections within 45 days. Reinfection appeared to be low during this time; however, previous seroposi tivity did not prevent colonization.