Influence of temperature on Cryptosporidium parvum oocyst infectivity in river water samples as detected by tissue culture assay.
Cryptosporidium parvum oocysts were stored in 1-ml aliquots of filtered river water at -20, 4, 10, and 21-23 C in the dark. Oocysts were also added to filter-sterilized river water samples and stored at 21-23 C. The infectivity of oocysts stored under different conditions was assayed at weekly intervals through infection of human adenocarcinoma ileocecal (HCT-8) cell monolayers. Wells containing between 10 and 100 foci of infection were enumerated by immunofluorescent microscopy, and the number of infective oocysts was calculated. No infectious oocysts were detected after 1 wk at -20 C. The number of infective oocysts stored at 4 C decreased 5-fold, and the number of those stored at 10 C decreased 2.5-fold after 14 wk. The infectivity of oocysts stored in potassium dichromate (positive control) at 4 C decreased 2-fold over 14 wk. The number of infective oocysts in filter-sterilized and non-filter-sterilized river water stored at 21-23 C decreased by 3.3 and 2.6 log units, respectively, over 12 wk, and no foci of infection were detected at 14 wk. The results show that as temperature increased from 4 to 23 C, the duration of oocyst infectivity decreased.
Pokorny
Nicholas J
NJ
Department of Environmental Biology, University of Guelph, Ontario, Canada.
Weir
Susan C
SC
Carreno
Ramon A
RA
Trevors
Jack T
JT
Lee
Hung
H
D000818:Animals; D003080:Cold Temperature; D003457:Cryptosporidiosis / Q000469:parasitology; D016785:Cryptosporidium parvum / Q000254:growth & development / Q000472:pathogenicity*; D005456:Fluorescent Dyes / Q000737:chemistry; D005618:Fresh Water / Q000469:parasitology*; D006801:Humans; D008856:Microscopy, Fluorescence; D009864:Ontario; D014407:Tumor Cells, Cultured; D014881:Water Supply
D005456:Fluorescent Dyes