title: Intact Cryptosporidium parvum oocysts isolated after in vitro excystation are infectious to neonatal mice.
abstract: In vitro excystation is often used as a measure of viability of encysted protozoan parasites. Parasites that do not excyst in vitro are assumed to be non-viable and non-infectious, whereas those that do excyst are assumed viable. To test the validity of these assumptions, Cryptosporidium parvum oocysts were excysted in vitro using two different excystation protocols, and the non-excysted intact oocysts were isolated using flow cytometry. Non-excysted sorted oocysts readily infected neonatal CD-1 mice. Increasing the duration of the excystation assays from 1 h to 3 h resulted in a higher percent of excysted oocysts, but the remaining non-excysted parasites were still capable of infecting neonatal CD-1 mice. Our results suggest that in vitro excystation is not an accurate measure of the viability or infectious potential of C. parvum oocysts.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alta, Canada.
authors.forename: N F
authors.initials: NF
authors.lastname: Neumann
authors.forename: L L
authors.initials: LL
authors.lastname: Gyürék
authors.forename: G R
authors.initials: GR
authors.lastname: Finch
authors.forename: M
authors.initials: M
authors.lastname: Belosevic
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016785:Cryptosporidium parvum / Q000472:pathogenicity*; D005434:Flow Cytometry; D008297:Male; D051379:Mice