title: Impact of bathers on levels of Cryptosporidium parvum oocysts and Giardia lamblia cysts in recreational beach waters.
abstract: Recreational beach water samples collected on weekends and weekdays during 11 consecutive summer weeks were tested for potentially viable Cryptosporidium parvum oocysts and Giardia lamblia cysts using the multiplexed fluorescence in situ hybridization (FISH) method. The levels of oocysts and cysts on weekends were significantly higher than on the weekdays (P<0.01). Concentrations of oocysts in weekend samples (n=27) ranged from 2 to 42 oocysts/L (mean: 13.7 oocysts/L), and cyst concentration ranged from 0 to 33 cysts/L (mean: 9.1 cysts/L). For the samples collected on weekdays (n=33), the highest oocyst concentration was 7 oocysts/L (mean: 1.5 oocysts/L), and the highest cyst concentration was 4 cysts/L (mean: 0.6 cysts/L). The values of water turbidity were significantly higher on weekends than on weekdays, and were correlated with the number of bathers and concentration of C. parvum oocysts and G. lamblia cysts (P<0.04). The study demonstrated positive relationships between number of bathers and levels of waterborne C. parvum oocysts and G. lamblia cysts in recreational beach water. It is essential to test recreational waters for Cryptosporidium and Giardia when numbers of bathers are greatest, or limit the number of bathers in a recreational beach area.
authors.affiliation: Department of Environmental Health Sciences, Division of Environmental Health Engineering, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD 21205, USA. dsunderland@jhsph.edu
authors.forename: Deirdre
authors.initials: D
authors.lastname: Sunderland
authors.forename: Thaddeus K
authors.initials: TK
authors.lastname: Graczyk
authors.forename: Leena
authors.initials: L
authors.lastname: Tamang
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Breysse
mesh_terms: D000818:Animals; D001493:Bathing Beaches; D016785:Cryptosporidium parvum / Q000302:isolation & purification*; D004784:Environmental Monitoring; D016829:Giardia lamblia / Q000302:isolation & purification*; D006801:Humans; D033661:Oocysts; D014871:Water Microbiology; D014873:Water Pollutants / Q000302:isolation & purification*
chemical_list: D014873:Water Pollutants