title: Cryptosporidium hominis: experimental challenge of healthy adults.
abstract: Cryptosporidium hominis causes diarrhea in humans and has been associated with community outbreaks. This study describes the infectivity, illness, and serologic response after experimental challenge of 21 healthy adult volunteers with 10-500 C. hominis (TU502) oocysts. Sixteen subjects (76.2%) had evidence of infection; the 50% infectious dose (ID(50)) was estimated to be 10-83 oocysts using clinical and microbiologic definitions of infection, respectively. Diarrhea occurred in 40% of subjects receiving 10 oocysts with a stepwise increase to 75% in those receiving 500 oocysts. A serum IgG response was seen in those receiving more than 30 oocysts. Greatest responses were seen in volunteers with diarrhea and oocyst shedding. Volunteers with no evidence of infection had indeterminant or negative IgG responses. Cryptosporidium hominis 10 oocysts) and is clinically is infectious for healthy adults (ID(50) = similar to C. parvum-induced illness. In contrast to C. parvum, C. hominis elicted a serum IgG response in most infected persons.
authors.affiliation: The University of Texas Health Science Center at Houston, School of Public Health and Medical School, Houston, Texas 77030, USA. Cynthia.L.Chappell@uth.tmc.edu
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Chappell
authors.forename: Pablo C
authors.initials: PC
authors.lastname: Okhuysen
authors.forename: Rebecca
authors.initials: R
authors.lastname: Langer-Curry
authors.forename: Giovanni
authors.initials: G
authors.lastname: Widmer
authors.forename: Donna E
authors.initials: DE
authors.lastname: Akiyoshi
authors.forename: Sultan
authors.initials: S
authors.lastname: Tanriverdi
authors.forename: Saul
authors.initials: S
authors.lastname: Tzipori
mesh_terms: D000328:Adult; D000818:Animals; D003457:Cryptosporidiosis / Q000276:immunology* / Q000469:parasitology* / Q000635:transmission; D016785:Cryptosporidium parvum / Q000276:immunology / Q000472:pathogenicity*; D003967:Diarrhea / Q000276:immunology* / Q000469:parasitology; D004198:Disease Susceptibility; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007928:Lethal Dose 50; D010270:Parasite Egg Count; D014867:Water / Q000469:parasitology*; D014881:Water Supply
chemical_list: D007074:Immunoglobulin G; D014867:Water