Rapidly measured indicators of recreational water quality and swimming-associated illness at marine beaches: a prospective cohort study

Abstract

IntroductionIn the United States and elsewhere, recreational water quality is monitored for fecal indicator bacteria to help prevent swimming-associated illnesses. Standard methods to measure these bacteria take at least 24 hours to obtain results. Molecular approaches such as quantitative polymerase chain reaction (qPCR) can estimate these bacteria faster, in under 3 hours. Previously, we demonstrated that measurements of the fecal indicator bacteria Enterococcus using qPCR were associated with gastrointestinal (GI) illness among swimmers at freshwater beaches. In this paper, we report on results from three marine beach sites.MethodsWe interviewed beach-goers and collected water samples at marine beaches affected by treated sewage discharges in Mississippi in 2005, and Rhode Island and Alabama in 2007. Ten to twelve days later, we obtained information about gastrointestinal, respiratory, eye, ear and skin symptoms by telephone. We tested water samples for fecal indicator organisms using qPCR and other methods.ResultsWe enrolled 6,350 beach-goers. The occurrence of GI illness among swimmers was associated with a log10-increase in exposure to qPCR-determined estimates of fecal indicator organisms in the genus Enterococcus (AOR = 2.6, 95% CI 1.3-5.1) and order Bacteroidales (AOR = 1.9, 95% CI 1.3-2.9). Estimates of organisms related to Clostridium perfringens and a subgroup of organisms in the genus Bacteroides were also determined by qPCR in 2007, as was F+ coliphage, but relationships between these indicators and illness were not statistically significant.ConclusionsThis study provides the first evidence of a relationship between gastrointestinal illness and estimates of fecal indicator organisms determined by qPCR at marine beaches.

Acute Gastroenteritis and Recreational Water: Highest Burden Among Young US Children

“…24 We did not consider individuals who reported an episode of diarrhea or vomiting in the 3 days before enrollment at risk. Secondary outcomes for attributable risk calculations included incident gastrointestinal illness, defined consistently with previous studies [10][11][12][13] as (1) diarrhea, (2) vomiting, (3) nausea and stomachache, or (4) nausea or stomachache and missed regular activities as a result of illness; days of missed work, school, or vacation owing to any gastrointestinal illness; days of missed paid work owing to gastrointestinal illness; and medical consultations associated with gastrointestinal illness, including telephone consultations, inpatient or outpatient care, and emergency room visits. For days of missed work, school, or vacation, we included days missed by individuals aged 13 years or older who were caring for other family members even if they were not ill themselves.…”

“…[7][8][9][10][11][12][13][14] The beaches represented a range of recreational water conditions across the United States: 4 freshwater beaches were in the Great Lakes region, 4 marine beaches were in Southern California, and the remaining 5 marine beaches were spread along the Gulf Coast, Eastern Seaboard, and Puerto Rico. Nine of the beaches were located near a known source of treated sewage discharge (referred to as "point source"-affected beaches), and the remaining 4 beaches had more diffuse contamination from urban runoff (details are available in Appendix A, available as a supplement to the online version of this article at http://www.…”

“…First, we determined whether individuals entered the water and, if so, their level of water contact. Consistent with previous studies, [7][8][9][10][11][12][13][14] we used graded exposure levels: body immersion swimming (waist depth or greater), head immersion, and swallowed water. The categories were not exclusive; for example, individuals who swallowed water may have been body immersion swimmers.…”

“…Recent waterbody closures at Brazilian Olympic venues 4 and Waikiki beach, Hawaii 5 illustrate recreational water contamination's public health and economic reach. Several cohort studies and randomized trials have measured swimming-related health risks and risks associated with exposure to waters containing elevated fecal indicator bacteria levels, [6][7][8][9][10][11][12][13][14][15][16][17] but individual studies are usually too small to estimate the public health burden associated with water exposure with respect to missed daily activities (work, school, vacation) or medical visits and hospitalizations that result from gastroenteritis. Moreover, individual studies have not typically enrolled enough swimmers to estimate risks separately for children.…”

“…2,21 We conducted a pooled analysis of 13 prospective cohorts in the United States (84 411 participants). [7][8][9][10][11][12][13][14] We coordinated studies to ensure similar designs and measurement methods. This approach enabled us to calculate summary estimates for gastroenteritis risk and related medical and daily activity impacts associated with recreational water exposure and Enterococcus levels; it also enabled us to report for the first time, to our knowledge, separate estimates for children aged 0 to 4 and 5 to 10 years.…”