Seroprevalence of cryptosporidial antibodies during infancy, childhood, and adolescence.

Cryptosporidium parvum causes mild to moderately severe diarrhea in immunocompetent individuals. Cryptosporidial antibodies in the sera of 803 children seen at Children's Hospital of Oklahoma were measured by means of an ELISA. Thirteen percent of children younger than 5 years of age were seropositive for antibodies to C. parvum. The seropositivity rate for children who attended day-care facilities was higher than that for those who did not. In addition, children in this age group with a history of recent diarrhea were seropositive at a higher rate than were children without diarrhea. Thirty-eight percent of children (5-13 years of age) and 58% of adolescents (14-21 years of age) were seropositive for antibodies to C. parvum. Blacks and Native Americans in these age groups had higher seropositivity rates than did White non-Hispanics. There were no differences in seropositivity rates between sexes or between residents of the largest urban counties in Oklahoma and residents of the more rural counties. Exposure to C. parvum during childhood is common in Oklahoma. Socioeconomic factors may play a role in early exposure to this protozoal pathogen.