Academic journal article Canadian Journal of Public Health

The Relationship between E. Coli Indicator Bacteria in Well-Water and Gastrointestinal Illness in Rural Families

Academic journal article Canadian Journal of Public Health

The Relationship between E. Coli Indicator Bacteria in Well-Water and Gastrointestinal Illness in Rural Families

Article excerpt


Objectives: To determine the relationship between consumption of E. coli contaminated well-water and gastrointestinal illness in rural families.

Methods: One hundred and eighty-one families with well-water as a drinking source participated in a one-year follow-up study. Water was tested for E. coli bacteria and health outcomes were monitored for household members.

Results: E. coli in well-water was significantly associated with gastrointestinal illness in family members, however the relationship was modified by the distance from the septic tank to the well. E. coli had an odds ratio of 2.16 [95% CI 1.04, 4.42] if the septic tank was greater than 20 metres from the well and 0.46 [95% CI 0.07, 2.95] if the septic tank was within 20 metres.

Conclusions: Consumption of contaminated well-water is associated with gastrointestinal illness. E coli can be a useful marker for detecting wells that pose a potential public health problem in rural areas.


Objectifs: Etudier l'association possible entre la consommation d'eau de puits contaminee par. E. coli et l'occurrence de maladies gastro-intestinales dans les familles rerales.

Methodes: Cent quatre-vingt et une familles ayant un puits comme source d'eau de consommation ont participe a une etude s'echelonnant sur une annee. L'eau de puits a ete analysee pour la recherche E. coli et l'etat de sante de chaque membre de la famille a ete suivi.

Resultats: La presence de E. coli dans l'eau de puits etait significativement associee aux maladies gastro-intestinales chez les membres de la famille quoique cette relation etait dependante de la distance entre le puits et la fosse septique. Le rapport de cotes du E. coli etait de 2,16 [95% IC 1,04, 4,42] si la fosse septique etait a plus de 20 metres to 0,46 [95% IC 0,07, 2,95} si la fosse septique etait a moins de 20 metres du puits.

Conclusions: La consommation d'eau de puits souillee est associee aux maladies gastro-intestinales. Le E. coli peut etre un indicateur utile pour detecter les puits qui posent un probleme potentiel de sante publique dans les zones rurales.

A groundwater quality survey that sampled farm wells across Ontario in 19911992 found that about 30% of the farm wells exceeded the safety standard for coliform bacteria.1 Indicators of fecal contamination, such as coliform, fecal coliform, and Escherichia coli counts, have been used to determine the safety of drinking water.2 A positive association between gastrointestinal illness and drinking water measures, such as coliform bacterial counts and turbidity, has been described for rural as well as urban populations.3-6 Additionally, relative to the population served, wellwater sources are involved in a large proportion of reported outbreaks associated with drinking water in North America.7,

The health effects among rural families that rely on individual wells for drinking water have not been reported. Given the high level of exposure to indicator bacteria and evidence that exposure is associated with illness, there is, potentially, a substantial health risk associated with drinking substandard well-water. Therefore, the purpose of this longitudinal study was to determine if the presence of E. coli indicator bacteria in well-water is associated with gastrointestinal illness in rural Ontario families.


Study population

The families in this study were selected from participants in the Ontario Farm Groundwater Quality Survey (19911992).' Based on the results of the 19911992 survey, 442 families from southern Ontario were identified for potential inclusion in this study, and were classified as having well-water with either "contamination" or "no contamination". The "no contamination" group (N = 247) consisted of families that had no coliform bacteria isolated in either of the 1991 and 1992 samples. The "contamination" group (N = 195) consisted of families that had coliform bacteria identified from water samples on both tests with at least one wellwater sample exceeding established bacteriological standards (exceeding 5 colonies of coliform bacteria per 100 ml of water or any E. …

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