2 abstracts on correlation between bathers and pathogens (and sediment resuspension)

["Shannon Briggs" <briggssl@michigan.gov>]

Water Research. 2007; 41(15):3483-3489. 
Impact of Bathers on Levels of Cryptosporidium Parvum Oocysts and
Giardia Lamblia Cysts in Recreational Beach Waters.  
Sunderland, Deirdre; Graczyk, Thaddeus K.; Tamang, Leena, and Breysse,
Patrick N. 
http://www.sciencedirect.com/science/article/B6V73-4NR187Y-2/2/293dbfc13975246c99aa8bf75fe07d47


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.

Appl. Environ. Microbiol. 2007; 73(13):4095-4099.  
Quantitative Evaluation of the Impact of Bather Density on Levels of
Human-Virulent Microsporidian Spores in Recreational Water. 
Graczyk, Thaddeus K.; Sunderland, Deirdre; Tamang, Leena; Shields,
Timothy M.; Lucy, Frances E., and Breysse, Patrick N. 
 http://aem.asm.org/cgi/content/abstract/73/13/4095 

Abstract: Microsporidial gastroenteritis, a serious disease of
immunocompromised people, can have a waterborne etiology. During summer
months, samples of recreational bathing waters were tested weekly for
human-virulent microsporidian spores and water quality parameters in
association with high and low bather numbers during weekends and
weekdays, respectively. Enterocytozoon bieneusi spores were detected in
59% of weekend (n = 27) and 30% of weekday (n = 33) samples, and
Encephalitozoon intestinalis spores were concomitant in a single weekend
sample; the overall prevalence was 43%. The numbers of bathers, water
turbidity levels, prevalences of spore-positive samples, and
concentrations of spores were significantly higher for weekend than for
weekday samples; P values were <0.001, <0.04, <0.03, and <0.04,
respectively. Water turbidity and the concentration of waterborne spores
were significantly correlated with bather density, with P values of
<0.001 and <0.01, respectively. As all water samples were collected on
days deemed acceptable for bathing by fecal bacterial standards, this
study reinforces the scientific doubt about the reliability of bacterial
indicators in predicting human waterborne pathogens. The study provides
evidence that bathing in public waters can result in exposure to
potentially viable microsporidian spores and that body contact
recreation in potable water can play a role in the epidemiology of
microsporidiosis. The study indicates that resuspension of bottom
sediments by bathers resulted in elevated turbidity values and implies
that the microbial load from both sediments and bathers can act as
nonpoint sources for the contamination of recreational waters with
Enterocytozoon bieneusi spores. Both these mechanisms can be considered
for implementation in predictive models for contamination with
microsporidian spores.

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