A serological survey of college students for antibody to Cryptosporidium before and after the introduction of a new water filtration plant

In April 1997, a large city in the northeastern United States changed their drinking water treatment practices. The city, which previously provided on ly chlorination for their surface water sources added filtration in additio n to chlorination. To assess whether Cryptosporidium infections rates decli ned following filtration, we tested serological responses to 15/17-kDa and 27-kDa Cryptosporidium antigens among 107 community college students 1 mont h before and 225 students 5 months after filtration. Results suggest that l evels of Cryptosporidium infections did not decline following water filtrat ion. However, seasonal changes in other exposures may have confounded the f indings. Swimming in a lake, stream or public pool and drinking untreated w ater from a lake or stream predicted a more intense response to one or both markers. Residence in the city, not drinking city tap water or drinking bo ttled water, gender, travel or exposure to pets, young pets, diapers or a h ousehold child in day care were not found to be predictive of more or less intense serological responses for either the 15/17-kDa and 27-kDa antigen.