Using rapid indicators for Enterococcus to assess the risk of illness after exposure to urban runoff contaminated marine water

Abstract

Background Traditional fecal indicator bacteria (FIB) measurement is too slow (>18 hr) for timely swimmer warnings. Objectives Assess relationship of rapid indicator methods (qPCR) to illness at a marine-beach impacted by urban-runoff. Methods We measured baseline and two-week health in 9525 individuals visiting Doheny Beach 2007-08. Illness rates were compared (swimmers vs. non-swimmers). FIB measured by traditional (Enterococcus spp. by EPA Method 1600 or Enterolert™, fecal coliforms, total coliforms) and three rapid qPCR assays for Enterococcus spp. (Taqman, Scorpion-1, Scorpion-2) were compared to health. Primary bacterial source was a creek flowing untreated into ocean; the creek did not reach the ocean when a sand berm formed. This provided a natural experiment for examining FIB-health relationships under varying conditions. Results We observed significant increases in diarrhea (OR1.90, 95% CI 1.29-2.80 for swallowing water) and other outcomes in swimmers compared to non-swimmers. Exposure (body immersion, head immersion, swallowed water) was associated with increasing risk of gastrointestinal illness (GI). Daily GI incidence patterns were different: swimmers (2-day peak ) and non-swimmers (no peak). With berm-open, we observed associations between GI and traditional and rapid methods for Enterococcus; fewer associations occurred when berm status was not considered. Conclusions We found increased risk of GI at this urban-runoff beach. When FIB source flowed freely (berm-open), several traditional and rapid indicators were related to illness. When FIB source was weak (berm-closed) fewer illness-associations were seen. These different relationships under different conditions at a single beach demonstrate the difficulties using these indicators to predict health risk.

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.…”