Abstract
The use of recreational water of poor microbiological quality may negatively impact on the health of people that are exposed during a diversity of leisure activities. Microbiological contamination of recreational waters may arise from various human and animal faecal sources, but the microbiological quality of bathing water may also deteriorate
... read more
due to proliferation of micro-organisms of non-faecal origin, such as Trichobilharzia and Vibrio. Long-term surveillance of recreational water related illness in The Netherlands showed that most recreational waterborne outbreaks comprised of skin conditions (48%) and gastroenteritis (31%). The number of outbreaks in a bathing season was strongly associated with weather conditions, with higher numbers in warm summers, but did not decline over the years, while compliance with European bathing water legislation increased. Current European bathing water quality standards are guided by faecal contamination events, but do not directly address waterborne pathogens of either faecal or non-faecal origin. The presence of Trichobilharzia, Vibrio, Cryptosporidium and Giardia was demonstrated in Dutch bathing waters compliant with European bathing water legislation, suggesting that monitoring of faecal indicator parameters and striving for compliance with required water quality standards may not sufficiently protect bathers from exposure to faecal and non-faecal waterborne pathogens. Cases of swimmers’ itch, caused by larvae of the parasite Trichobilharzia, are one of the most frequently reported health conditions resulting from bathing water exposure in The Netherlands. Epidemiological data from outbreaks of swimmers’ itch suggested that longer and more frequent exposure to suspected water resulted in increased reporting of symptoms. The detection of the parasite in the suspected bathing water guides interventions to prevent further cases, but is often difficult. A novel approach of simultaneously testing of collected snails and water samples from implicated bathing waters enhances the chance of parasite detection. Vibrio infections through exposure to Dutch bathing waters seem rare, but may be underestimated. Vibrio was present at four official Dutch bathing sites, albeit in low numbers, and more samples were positive at elevated water temperatures. The common occurrence of Vibrio spp. stresses the need to provide information on this micro-organism particularly to risk groups, such as people with underlying illness or open wounds. In addition, low numbers of Cryptosporidium and Giardia in recreational lakes in Amsterdam, compliant with European bathing water legislation, posed infection risks ranging between 0.01% and 0.05% for Cryptosporidium and between 0.0004% and 0.01% for Giardia, with highest infection risks for children. Infection risk assessment was improved by using newly generated exposure data collected in a study among swimmers in freshwater, seawater and swimming pools through questionnaires administered to approximately 19000 persons representing the general Dutch population. Monitoring of faecal indicator parameters and striving for compliance with standards for these parameters in European bathing water legislation does not prevent all outbreaks of recreational waterborne disease. A more effective approach for adequate protection of bathers may be a combination of the use of information available from bathing water profiles, risk assessment and high frequency monitoring using rapid molecular detection methods, addressing both faecal and non-faecal waterborne pathogens
show less
