Inactivation of Giardia muris cysts using medium-pressure ultraviolet radiation in filtered drinking water

The effect of medium pressure ultraviolet radiation on Giardia muris was studied using a collimated beam apparatus with filtered surface water from the Grand River, Kitchener, Ontario, Canada. UV doses ranged from 5 to 83 mJ/cm2 and resulted in 2–3 log-units of reduction in infectivity measured by a C3H/HeN mouse infectivity model. In vitro excystation and nucleic acid staining with Live/Dead BacLight™ greatly underestimated the inactivation of Giardia when compared with animal infectivity. Medium pressure ultraviolet radiation is a potential alternative to conventional chemical disinfection methods.