title: Genetic polymorphism among Cryptosporidium parvum isolates: evidence of two distinct human transmission cycles.
abstract: We report the results of molecular analysis of 39 isolates of Cryptosporidium parvum from human and bovine sources in nine human outbreaks and from bovine sources from a wide geographic distribution. All 39 isolates could be divided into either of two genotypes, on the basis of genetic polymorphism observed at the thrombospondin-related adhesion protein (TRAP-C2) locus. Genotype 1 was observed only in isolates from humans. Genotype 2, however, was seen in calf isolates and in isolates from a subset of human patients who reported direct exposure to infected cattle or consumed items thought to be contaminated with cattle faces. Furthermore, experimental infection studies showed that genotype 2 isolates were infective to mice or calves under routine laboratory conditions, whereas genotype 1 isolates were not. These results support the occurrence of two distinct transmission cycles of C. parvum in humans.
authors.affiliation: University of Michigan, Ann Arbor, USA.
authors.forename: M M
authors.initials: MM
authors.lastname: Peng
authors.forename: L
authors.initials: L
authors.lastname: Xiao
authors.forename: A R
authors.initials: AR
authors.lastname: Freeman
authors.forename: M J
authors.initials: MJ
authors.lastname: Arrowood
authors.forename: A A
authors.initials: AA
authors.lastname: Escalante
authors.forename: A C
authors.initials: AC
authors.lastname: Weltman
authors.forename: C S
authors.initials: CS
authors.lastname: Ong
authors.forename: W R
authors.initials: WR
authors.lastname: Mac Kenzie
authors.forename: A A
authors.initials: AA
authors.lastname: Lal
authors.forename: C B
authors.initials: CB
authors.lastname: Beard
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D016785:Cryptosporidium parvum / Q000145:classification / Q000235:genetics*; D016054:DNA, Protozoan / Q000032:analysis / Q000737:chemistry; D005838:Genotype; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
chemical_list: D016054:DNA, Protozoan