The Walkerton Health Study

Richards, A. (2005) Canadian Nurse, 101 (5); 16-21.

In May 2005 the Walkerton, Ontario municipal water supply was contaminated with Escherichia coli 0157:H7, Campylobacter , Salmonella and other bacterial pathogens. As a result there were at least 2,300 cases of gastrointestinal illness (GI) along with 28 confirmed cases of haemolytic uremic syndrome (HUS), a very severe kidney complication.

The Walkerton Health Study (WHS) was established after the provincial Ministry of Health and Long-term Care determined that a study should be undertaken on the long-term health effects associated with drinking contaminated water. The Walkerton Health Study is a seven-year project and was established as a screening and treatment clinic to identify and treat people with asymptomatic disease as well as those with symptoms and complications related to E. Coli 0157:H7, Campylobacter or both and to study long-term health effects.

The general aim of the screening clinics is to determine by yearly screening the long-term burden of illness attributed to water contamination, and more specifically to reduce and prevent long-term complications by identifying and referring individuals at risk for more detailed investigation and treatment. A survey questionnaire is used as part of the screening process. The questionnaire gathers information on outcomes such as renal, GI, neurological, arthritic and psychological complaints. Also general demographic information is collected on the participants, their exposure to contaminated water and their water source. There are questions on medical history, family history, illness at the time of the outbreak, previous contact with farm animals and pharmaceutical use. Information gathered is cross-referenced with records obtained from family physicians and hospitals. Participants also have their weight, height and blood pressure (BP) measured and blood and urine tests. On the basis of their survey answers and blood pressure measurements, participants are then referred to specialists as required. Critical value triggers for laboratory results and BP measurements set by investigators are used to initiate appropriate action.

Findings have been gathered from the first three years of the study. During the first year of the clinic 3,959 people completed the screening. There were 399 participants identified as having significant GI complaints. Most of those seen by a GI specialist were thought to have post-infectious Irritable Bowel Syndrome (IBS). An experimental investigation of intestinal permeability was undertaken in a subgroup of IBS cases and normal controls. It was found that two years after the waterborne outbreak of acute gastroenteritis, IBS symptoms were associated with increased intestinal permeability. Also some participants were still suffering from post-traumatic stress disorder with the most common diagnoses being anxiety and depression. There were a small number of participants with newly diagnosed elevated BPs or abnormal kidney function, and some of these had worsening conditions associated with the water contamination.

In the second year of the clinic, 3,373 people completed the screening and the focus was on diabetes mellitus. In the third year 3,461 people completed the screening and the focus was on bowel problems. A booklet was specifically written on IBS for the people of Walkerton to provide participants with information. There have been 4238 participants tested at least once for diabetes, with 45 newly diagnosed diabetics found and 51 other participants thought to be in the pre-diabetic range. There were a group of people identified who are producing unusually large volumes of urine with protein. It is possible that over time, this condition may lead to kidney damage and therefore these people are being asked to complete a series of urine tests.

The Walkerton Health Study is the largest ever follow up study of people exposed to pathogenic E. coli infection, and information from this project will increase understanding of health risks associated with contaminated water.