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Household Epidemiology of Cryptosporidium parvum Infection in an Urban Community in Northeast Brazil

Robert D. Newman, MD; Shu-Xian Zu, MD; Tadesse Wuhib, MD; Aldo A. M. Lima, MD, PhD; Richard L. Guerrant, MD; and Cynthia L. Sears, MD
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From Johns Hopkins University School of Medicine, Baltimore, Maryland; Unidade Pesquisas Clinicas, Universidade Federal do Ceara, Fortaleza, Ceara, Brazil; the University of Virginia School of Medicine, Charlottesville, Virginia. Requests for Reprints: Cynthia L. Sears, MD, Johns Hopkins University School of Medicine, Ross 933, 720 Rutland Avenue, Baltimore, MD 21205-2196. Acknowledgments: The authors thank Sayonara Alencar, Luza Sousa de Melo, and Lourdes P. Rodrigues for their invaluable assistance in the field; Isabel McAuliffe, Jania Teixeira, Maria do Carmo Nunes de Pinho, Leah Barrett, Conceicao Nogueira Raulino, and Ivo Castro for their laboratory assistance; Dr. Clovis Martins for his laboratory assistance at the University of Virginia; Dr. Ron Fayer at the United States Department of Agriculture for providing purified Cryptosporidium oocysts; Dr. L.P. Ungar at the National Institutes of Health for discussions of study design; and Dr. Howard Lederman at The Johns Hopkins University School of Medicine for reviewing the data. Grant Support: In part by NIH ICIDR grant PO1-A126512 02 and by a grant (to RDN) from the Dean's office of the Johns Hopkins University School of Medicine.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1994;120(6):500-505. doi:10.7326/0003-4819-120-6-199403150-00009
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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 acid-fast and auramine-stained stool smears.

Measurements: Three stool samples (at 0, 2, and 6 weeks after identification of the index case) and two serum samples (0 and 6 weeks) were collected from each family member in households with an index case of Cryptosporidium infection.

Results: 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 examination 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, 191 (94.6%) had evidence of antibodies (either IgM or IgG) to Cryptosporidium.

Conclusions: Cryptosporidium parvum is highly transmissible and infective in the family setting, with transmission rates similar to other highly infectious enteric pathogens such as Shigella species. These data are cause for added concern because of the rapidly increasing rate of seropositivity for human immunodeficiency virus.





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