Quantitative Evaluation of the Impact of Bather Density on Levels of Human-Virulent Microsporidian Spores in Recreational Water

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 humanvirulent 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.

Relationships among bather density, levels of human waterborne pathogens, and fecal coliform counts in marine recreational beach water

“…Water quality parameters such as temperature, dissolved O 2 , salinity, and conductivity were measured using a portable meter YSI Model #85 (YSI Incorporated, Yellow Springs, OH, USA), and water turbidity was determined by a portable DR/890 Colorimeter (Hach, Loveland, CO, USA) ( Table 1). The numbers of bathers were counted and assigned a density score as described previously (Graczyk et al 2007b) ( Table 1). The 24-h rainfall data and tide levels corresponding to the water collection dates were obtained electronically (NRDC 2005) ( Table 1).…”

Municipal wastewater treatment plants as removal systems and environmental sources of human-virulent microsporidian spores

“…Microsporidian spores have been found throughout the bathing season in marine recreational waters (Graczyk et al 2007c;Lucy et al 2008) and in a range of lakes and rivers used for drinking water abstraction and recreation (Graczyk et al 2004;Lucy et al 2008). Discharge of effluents from wastewater treatment plants is an important point source of microsporidian spores in surface waters used for drinking water abstraction and recreation (Lucy et al 2008); both E. intestinalis and E. bieneusi spores have been identified in such effluents (Dowd et al 1998;Graczyk et al 2007a).…”

Bather density and levels of Cryptosporidium, Giardia, and pathogenic microsporidian spores in recreational bathing water

“…As fecal coliforms in recreational bathing waters originate from bather-induced resuspension of bottom sediments (Hanes and Fosa 1970;Cheung et al 1991;Steward et al 2002) and from bathers themselves (Gerba 2000;Elmir et al 2007), crowded beach waters usually have the highest fecal coliform levels (Kay et al 1994;Elmir et al 2007). Information on relationships between bather density and the levels of other human enteropathogens is scant; however, recent studies indicate that such relationships exist for waterborne protozoan pathogens as well (Graczyk et al 2007b;Sunderland et al 2007). …”