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. 1997 Oct-Dec;3(4):567–573. doi: 10.3201/eid0304.970423

Genetic polymorphism among Cryptosporidium parvum isolates: evidence of two distinct human transmission cycles.

M M Peng 1, L Xiao 1, A R Freeman 1, M J Arrowood 1, A A Escalante 1, A C Weltman 1, C S Ong 1, W R Mac Kenzie 1, A A Lal 1, C B Beard 1
PMCID: PMC2640093  PMID: 9366611

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.

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Selected References

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