The role of breast milk in protecting urban Peruvian children against cryptosporidiosis.
To test the hypothesis that breast milk of nursing mothers may afford children protection against cryptosporidiosis, a prospective cohort study was carried out in the young peoples' community of San Juan de Miraflores near Lima, Peru. Mothers and newborn children were sorted into cohort groups based on the mothers' breast milk antibody response to Cryptosporidium sporozoites using an antibody-capture enzyme-linked immunosorbent assay to detect parasite-specific immunoglobulin A. Children were monitored for Cryptosporidium infection using an indirect immunofluorescence assay. Of 211 mothers enrolled in the study, 39 (18.5%) had high breast milk antibody titers, 107 (50.7%) had medium titers, and 65 (30.8%) had low titers. Sixty-one episodes of Cryptosporidium infection were detected in 50 children of these mothers. Eleven (22%) had mothers in the high antibody titer group, 20 (40%) had mothers in the medium titer group, and 19 (38%) had mothers in the low titer group. The prevalence of infection within children of each group was 0.17, 0.19 and 0.38 respectively. There was no significant difference in the prevalence or duration of infection among children of the different groups. The data does not support the notion that there is protection from Cryptosporidium infection afforded children whose mothers have demonstrable breast milk antibodies against the parasite.