Entamoeba histolytica infection in children and protection from subsequent amebiasis.

The contribution of amebiasis to the burden of diarrheal disease in children and the degree to which immunity is acquired from natural infection were assessed in a 4-year prospective observational study of 289 preschool children in an urban slum in Dhaka, Bangladesh. Entamoeba histolytica infection was detected at least once in 80%, and repeat infection in 53%, of the children who completed 4 years of observation. Annually there were 0.09 episodes/child of E. histolytica-associated diarrhea and 0.03 episodes/child of E. histolytica-associated dysentery. Fecal immunoglobulin A (IgA) anti-parasite Gal/GalNAc lectin carbohydrate recognition domain (anti-CRD) was detected in 91% (183/202) of the children at least once and was associated with a lower incidence of infection and disease. We concluded that amebiasis was a substantial burden on the overall health of the cohort children. Protection from amebiasis was associated with a stool anti-CRD IgA response. The challenge of producing an effective vaccine will be to improve upon naturally acquired immunity, which does not provide absolute protection from reinfection.