title: Occurrence of Cryptosporidium oocysts and Giardia cysts in raw waters in Norway.
abstract: OBJECTIVE
  This paper reports the first investigation into the occurrence of Cryptosporidium and Giardia in Norwegian raw water sources.
  
  
  METHODS
  Between June 1998 and October 1999, 408 raw water samples, collected from 147 different sites across Norway, were analysed for these parasites. Analysis was based upon US EPA Method 1623.
  
  
  RESULTS
  In 305 samples (75%), parasites were not detected. In 55 samples (13.5%), Cryptosporidium only was detected. In 38 samples (9%), Giardia only was detected. In 10 samples (2.5%) both Cryptosporidium and Giardia were detected. Of the sites sampled, parasites were not detected at 100 (68%) of them, Cryptosporidium only was detected at 20 (13.5%). Giardia only was detected at 11 (7.5%), and both Cryptosporidium and Giardia were detected at 16 (11%). Concentrations of parasites were low; usually one cyst/oocyst detected per 10 litres of water.
  
  
  CONCLUSIONS
  Significant associations were demonstrated for these samples between the detection of these parasites and (a) turbidity > or =2.0 NTU, and (b) high numbers of domestic animals within the catchment area. No association between seasonality and the occurrence of these parasites could be detected. The results are discussed in relation to other studies and the potential public health implications for Norway.
authors.affiliation: Department of Pharmacology, Microbiology and Food Hygiene, The Norwegian School of Veterinary Science, Oslo. Lucy.Robertson@veths.no
authors.forename: L J
authors.initials: LJ
authors.lastname: Robertson
authors.forename: B
authors.initials: B
authors.lastname: Gjerde
mesh_terms: D000818:Animals; D016009:Chi-Square Distribution; D003458:Cryptosporidium / Q000302:isolation & purification*; D005455:Fluorescent Antibody Technique; D005618:Fresh Water / Q000469:parasitology*; D005872:Giardia / Q000302:isolation & purification*; D009664:Norway; D018709:Statistics, Nonparametric; D014871:Water Microbiology