HOUSEHOLD EPIDEMIOLOGY OF CRYPTOSPORIDIUM-PARVUM INFECTION IN AN URBAN-COMMUNITY IN NORTHEAST BRAZIL

Objective: To examine the transmission of Cryptosporidium infection in households with an identified person with cryptosporidiosis. Design: Prospective cohort study. Setting: An urban slum in Fortaleza, Brazil. Participants: Thirty-one households with a child less than 3 years of age (index case) who was positive for Cryptosporidium parvum using ac id-fast and auramine-stained stool smears. Measurements: Three stool s amples (at 0, 2, and 6 weeks after identification of the index case) a nd two serum samples (0 and 6 weeks) were collected from each family m ember in households with an index case of Cryptosporidium infection. R esults: Forty-five percent of index cases of Cryptosporidium infection were associated with persistent (>14 days) diarrhea. Secondary cases of Cryptosporidium infection were identified either by stool examinati on or seroconversion in 18 (58%) of 31 households involving 30 persons , yielding an overall transmission rate of 19%. Of the 202 persons in this study with at least one serum sample available for analysis, 198 (94.6%) had evidence of antibodies (either IgM or IgG) to Cryptosporid ium. Conclusions: Cryptosporidium parvum is highly transmissible and i nfective in the family setting, with transmission rates similar to oth er highly infectious enteric pathogens such as Shigella species. These data are cause for added concern because of the rapidly increasing ra te of seropositivity for human immunodeficiency virus.