High sensitivity of children to swimming-associated gastrointestinal illness: results using a rapid assay of recreational water quality.
BACKGROUND
Culture-based methods of monitoring fecal pollution in recreational waters require 24 to 48 hours to obtain results. This delay leads to potentially inaccurate management decisions regarding beach safety. We evaluated the quantitative polymerase chain reaction (QPCR) as a faster method to assess recreational water quality and predict swimming-associated illnesses.


METHODS
We enrolled visitors at 4 freshwater Great Lakes beaches, and contacted them 10 to 12 days later to ask about health symptoms experienced since the visit. Water at the beaches was polluted by point sources that carried treated sewage. We tested water samples daily for Enterococcus using QPCR and membrane filtration (EPA Method 1600).


RESULTS
We completed 21,015 interviews and tested 1359 water samples. Enterococcus QPCR cell equivalents (CEs) were positively associated with swimming-associated gastrointestinal (GI) illness (adjusted odds ratio per 1 log10 QPCR CE =1.26; 95% confidence interval = 1.06-1.51). The association between GI illness and QPCR CE was stronger among children aged 10 years and below (1.69; 1.24-2.30). Nonenteric illnesses were not consistently associated with Enterococcus QPCR CE exposure, although rash and earache occurred more frequently among swimmers. Enterococcus QPCR CE exposure was more strongly associated with GI illness than Enterococcus measured by membrane filtration.


CONCLUSIONS
Measurement of the indicator bacteria Enterococci in recreational water using a rapid QPCR method predicted swimming-associated GI illness at freshwater beaches polluted by sewage discharge. Children at 10 years or younger were at greater risk for GI illness following exposure.
Wade
Timothy J
TJ
US Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Chapel Hill, NC 27711, USA. wade.tim@epa.gov
Calderon
Rebecca L
RL
Brenner
Kristen P
KP
Sams
Elizabeth
E
Beach
Michael
M
Haugland
Richard
R
Wymer
Larry
L
Dufour
Alfred P
AP
D000293:Adolescent; D000328:Adult; D001493:Bathing Beaches; D002648:Child; D002675:Child, Preschool; D016983:Enterococcus / Q000302:isolation & purification*; D004784:Environmental Monitoring / Q000379:methods; D062665:Epidemiological Monitoring; D005243:Feces / Q000382:microbiology; D005260:Female; D005618:Fresh Water / Q000382:microbiology*; D005767:Gastrointestinal Diseases / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D016133:Polymerase Chain Reaction / Q000379:methods*; D011446:Prospective Studies; D013550:Swimming; D014871:Water Microbiology; D014876:Water Pollution / Q000009:adverse effects