Studies on the resistance/reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts exposed to medium-pressure ultraviolet radiation.
The ex vivo and in vivo reactivation of Giardia muris cysts and Cryptosporidium parvum oocysts after exposure to different doses of ultraviolet (UV) radiation was determined using animal infectivity. The infectivity of UV-treated parasites stored for 1-4 days (G. muris) or 1-17 days (C. parvum) at room temperature in the dark was similar to that of organisms administered immediately after UV treatment, indicating that the parasites did not reactivate ex vivo. In contrast, we observed in vivo reactivation of G. muris in three of seven independent animal infectivity experiments, when parasites were treated with relatively low doses of medium-pressure UV (<25 mJ/cm(2)). Our observations indicate that G. muris cysts and C. parvum oocysts exposed to medium-pressure UV doses of 60 mJ/cm(2) or higher did not exhibit resistance to and/or reactivation following treatment. This suggests that when appropriate doses of UV are used, significant and permanent inactivation of these parasites may be achieved.
Belosevic
M
M
Department of Biological Sciences, CW-405 Biological Sciences Building, University of Alberta, Edmonton, Alberta, Canada T6G 2E9. mike.belosevic@ualberta.ca
Craik
S A
SA
Stafford
J L
JL
Neumann
N F
NF
Kruithof
J
J
Smith
D W
DW
D000818:Animals; D003457:Cryptosporidiosis / Q000469:parasitology / Q000503:physiopathology; D016785:Cryptosporidium parvum / Q000254:growth & development* / Q000472:pathogenicity / Q000528:radiation effects*; D004203:Disinfection / Q000379:methods; D004307:Dose-Response Relationship, Radiation; D005872:Giardia / Q000254:growth & development* / Q000472:pathogenicity / Q000528:radiation effects*; D005873:Giardiasis / Q000469:parasitology / Q000503:physiopathology; D051379:Mice; D008809:Mice, Inbred C3H; D014466:Ultraviolet Rays