Environmental sources of Cryptosporidium in an urban slum in northeastern Brazil

Cryptosporidium is an important cause of diarrheal disease in children worldwide. To elucidate the environmental sources of this parasite, we selected an urban slum in Fortaleza, Brazil, a community with a known high incidence of cryptosporidiosis, and examined both stool smears from household animals (n = 127) and filtrates from local water sources (n = 18) for Cryptosporidium oocysts. Because previous work in this community has demonstrated the seasonal nature of human infection with Cryptosporidium, collections were made separately for the dry and rainy seasons. Of the 64 stools collected during the dry season (September-December 1990), four (6.3%) were positive by acid-fast staining for Cryptosporidium. Of the 63 rainy season samples (March-May 1991), nine (14.3%) were positive. Overall, oocysts were detected in 13 (10.2%) of 127 animal stool samples. Freshwater samples were obtained from a variety of sources including open and closed wells, and running city water and then processed. Four of 18 samples (22.2%), including a sample from city water were positive by at least one of two staining techniques (acid-fast and immunofluorescence). In summary, animals may serve as a reservoir of Cryptosporidium, with potential for the contamination of immediate household water sources. These findings may help to explain the high incidence of cryptosporidiosis among infants in this impoverished community.