You are here:
LOW PRESSURE ULTRAVIOLET STUDIES FOR INACTIVATION OF GIARDIA MURIS CYSTS
Hayes*, S, M W. Ware, F W. Schaefer III, C Barnes, AND E W. Rice*. LOW PRESSURE ULTRAVIOLET STUDIES FOR INACTIVATION OF GIARDIA MURIS CYSTS. First International Congress on Ultraviolet Technologies, Washington, D.C, 6/14-16/2001.
This research was initiated to confirm and expand the current database for the inactivation of Giardia spp. using ultraviolet (UV) radiation. Initially, previous research that used in vitro excystation as the indicator for UV effectiveness was confirmed. Later, the in vitro excystation assay was employed in parallel with an animal infectivity assay. Using in vitro excystation as the viability indicator, doses as high as approximately 200 mJ/cm2 did not prevent some cysts from excysting, thus verifying earlier work. Based on excystation results, the first animal infectivity experiment was run at a UV dose of approximately 80 mJ/cm2. At this UV dose, no mice experienced infection. When the UV dose was lowered to approximately 8 mJ/cm2, again all animals were negative for infection. Infestivity assays of cysts exposed to approximately 1 mJ/cm2 showed no apparent inactivation. Duplicate runs at a UV dose of 1.9 mJ/cm2 yielded log reduction of -3.61 and -2.93. All positive and negative controls were within expectations for animal infectivity assays. The ID50 of the G. nuris isolate has been reported to be approximately 5 cysts and was confirmed. Results showed that in vitro excystation is not a reliable indicator of UV inactivation of G. muris cysts.