Cryptosporidium parvum - Specific antibody responses among children residing in Milwaukee during the 1993 waterborne outbreak

A major gastroenteritis outbreak among >400,000 residents of Milwaukee, Wis consin, in April 1993 was attributed to Cryptosporidium parvum oocysts in d rinking water. Plasma specimens obtained from children (6 months to 12 year s old) for routine blood lead level surveillance March-May 1993 were assaye d by ELISA for levels of IgG antibody against the immunodominant Triton-17 and 27-kDa C. parvum antigens. Over a 5-week period, the seroprevalence for antibodies to the 2 antigens increased from 15% to 82% and from 17% to 87% , respectively, in samples from children living in southern ZIP code areas (n = 218), whereas smaller increases (20% to 43% and 22% to 46%, respective ly) were noted among samples from children living in northern ZIP code area s (n = 335; P < .0001). The results demonstrate that C. parvum infection wa s much more widespread than previously appreciated and confirm that infecti on was associated with residence in the area served by the southern water t reatment plant.