The effect of gamma-irradiation on the viability of Cryptosporidium parvum.
Cryptosporidium parvum is 1 of the major causative organisms in waterborne diarrheal illness. Not only does C. parvum spread ubiquitously in our environment, it is also highly resistant to harsh environmental conditions and disinfectants. Therefore, a control measure for this protozoon is urgently required. This study investigated the effect of gamma-irradiation, in the range of 1,000-50,000 Gy, on the viability of C. parvum oocysts. Oocyst viability was determined by a combined indirect immunofluorescence and nucleic acid staining and animal infectivity study. The proportion of viable oocysts estimated by nucleic acid staining ranged from 94.2 to 89.4% in the 0- to 10,000-Gy groups, whereas it was reduced significantly to 58.6 or 45.7% in the 25,000- or 50,000-Gy group, respectively, at 24 hr postirradiation. In an animal infectivity study, oocysts irradiated with less than 10,000 Gy induced infections in mice wherein there were low numbers of oocysts per gram of feces amounting to 8-10.8% of the values in control mice, whereas with 50,000 Gy-irradiated oocysts, no oocysts were produced in the mice. This study suggests that at least 50,000 Gy of gamma-irradiation is necessary for the complete elimination of oocyst infectivity in mice.
Yu
J R
JR
Department of Parasitology, College of Medicine, Konkuk University, Chungju 380-701, South Korea.
Park
W Y
WY
D000818:Animals; D016785:Cryptosporidium parvum / Q000276:immunology / Q000502:physiology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D051379:Mice; D008810:Mice, Inbred C57BL; D013047:Specific Pathogen-Free Organisms