Animal Waste, Water Quality and Human Health

418Animal Waste, Water Quality and Human Healthseven to ten days later to determine if any episode of illness had occurred since theswimming experience.Swimmers were defined as individuals having significant exposure of upperbody orifices to beach water. Non-swimmers were beachgoers who did notimmerse their heads in beach water. The health endpoint, highly crediblegastrointestinal illness (HCGI), was defined as any one of the following:vomiting; diarrhoea with fever or a disability condition; and nausea orstomachache accompanied by a fever.We re-analyzed the data reported in Cheung et al. (1990) with respect to sourceand swimmer illness. The data for both beach water quality and health status fromthe two animal waste-affected sites were combined. This was also done with the datafrom six of the seven remaining beach sites that were contaminated by faecalwastes from sewer outfalls or stormwater drains. The seventh site was notincluded in the analysis because the faecal sources were described as being froma sewage outfall and a river, a mix of both human and animal faecalcontamination. The data extracted from Table 11.3 of the Cheung study areshown in Table 11.1. The average E. coli density at the animal faecescontaminatedbeach sites was 978 per 100 ml, with a range of 243 to 1714 E. coliper 100 ml. At the human sewage contaminated beach sites the average E. colidensity was 187 per 100 ml, with a range of 69 to 269 per 100 ml.Table 11.1 Analysis of data from Cheung et al. (1990) for swimmer-associatedgastroenteritis among beaches grouped by source of faecal contamination.FaecalsourceE. coli density(range, per100 ml)CategoryTotalnumberNumberillp Value 1Animal 243–1714 Swimmers 960 2 0.5246Non-swimmers 366 0Human 69–269 Swimmers 11,748 25 0.0418Non-swimmers 3368 21 p-value for the difference between swimmer/non-swimmer illness rates based on Fisher’sexact test.The total number of individuals who swam at the animal faeces-contaminatedbeach waters was 960; 366 non-swimmers at these beaches participated in astudy. In these two groups HCGI illness was observed in two of the swimmerswhile no HCGI illness was observed among the non-swimmers. At the beacheswith bathing waters contaminated by human sewage 11,748 swimmers