title: Solar UV reduces Cryptosporidium parvum oocyst infectivity in environmental waters.
abstract: OBJECTIVE
  To determine the effect of solar radiation on Cryptosporidium parvum in tap and environmental waters.
  
  
  RESULTS
  Outdoor tank experiments and a cell culture infectivity assay were used to measure solar inactivation of C. parvum oocysts in different waters. Experiments conducted on days with different levels of solar insolation identified rapid inactivation of oocysts in tap water (up to 90% inactivation within the first hour). Increased dissolved organic carbon content in environmental waters decreased solar inactivation. The role of solar ultraviolet (UV) in inactivation was confirmed by long-pass filter experiments, where UV-B was identified as the most germicidal wavelength. Reductions in oocyst infectivity following solar radiation were not related to a loss of excystation capacity.
  
  
  CONCLUSIONS
  Solar UV can rapidly inactivate C. parvum in environmental waters.
  
  
  CONCLUSIONS
  This is the first study to assess natural sunlight inactivation of C. parvum oocysts in surface waters and drinking water using an infectivity measure and determines the wavelengths of light responsible for the inactivation. The findings presented here provide valuable information for determining the relative risks associated with Cryptosporidium oocysts in aquatic environments and identify solar radiation as a critical process affecting the oocyst survival in the environment.
authors.affiliation: The Co-operative Research Centre for Water Quality and Treatment, Australian Water Quality Centre, SA Water Corporation, Salisbury, South Australia, Australia.
authors.forename: B J
authors.initials: BJ
authors.lastname: King
authors.forename: D
authors.initials: D
authors.lastname: Hoefel
authors.forename: D P
authors.initials: DP
authors.lastname: Daminato
authors.forename: S
authors.initials: S
authors.lastname: Fanok
authors.forename: P T
authors.initials: PT
authors.lastname: Monis
mesh_terms: D000818:Animals; D016785:Cryptosporidium parvum / Q000528:radiation effects*; D005618:Fresh Water; D033661:Oocysts / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*; D014881:Water Supply