Contamination of Drinking, Recreational and Irrigation Water by Escherichia coli

Contamination of Drinking, Recreational and Irrigation Water by Escherichia coli

Water, Health and Sanitation

PARA 515

March 30, 2017

Contamination of Drinking, Recreational and Irrigation Water by Escherichia coli

Escherichia coli abbreviated E. coli is a bacteria that is normally found in the intestine of warm-blood organisms including animals and humans (1,2). E. coli is a gram-negative, motile, facultative aerobe and non-spore forming rod-shaped bacterium (3). There are many strains of   E. coli and most of them are part of the healthy microbiota of humans and are non-pathogenic while some strains are pathogenic and can cause serious illness to humans and not to animals (2). The pathogenic strains of E. coli are associated with gastrointestinal infection and they are classified in six groups based on their virulence characteristics (2,3). The six groups are: enterohemorrhagic      E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), enteroaggreagtive E. coli (EAEC) and diffuse adherent E. coli (DAEC) (3). EHEC is the most frequent and severe cause of infection (2,3). The serotype E. coli O157:H7, which is the most common cause of foodborne and waterborne outbreaks, is part of the EHEC group (2,3). It was reported by the U.S. Centers for Diseases Control Prevention (CDC) that from 1992 to 2002, EHEC was the cause of 25% (16 of 64) of the gastrointestinal illness outbreaks for natural waters (3). In 14 of these 16 outbreaks, E. coli O157:H7 was the associated serotype (3).  

In order to be infected, less than 100 EHEC cells or sometimes only 50 cells are enough to cause infection (3). Hemorrhagic colitis characterized by bloody diarrhea, severe cramps and abdominal pain is the consequence of an infection with EHEC (3). The incubation period, which is the time before someone experiences the symptoms, is between 1 to 8 days and the infection duration is between 1 to 12 days (3). Generally people with hemorrhagic colitis recover completely, but in 2 to 8% of the cases the condition develops in hemolytic uremic syndrome, (HUS) a disease where red blood cells are massively destroyed, kidney failure is likely to occur and death is possible (3,4). Some people including children, elderly and immunocompromised persons are more at risk of developing HUS when they have hemorrhagic colitis (3).

EHEC is mainly found in the intestines of cattle, sheep, swine, goats and deer (4). During slaughter, E. coli found in the intestines of the animal will come in contact with the meat which will become contaminated (5). The bacteria are killed when the food is cooked properly, so raw and undercooked ground meat as well as unpasteurized milk can cause infection with E. coli (1,5). The infection can also be spread due to poor hygiene because an infected person who did not wash his hand properly and has a direct contact with food will cause cross-contamination of the food (1,5). As a result, another person who will eat the food will get infected. Infection can also be spread by person to person contact (5). Furthermore, consumption of raw fruits and vegetables is associated with increased risk of infection with E. coli because it is possible that the vegetables have been contaminated by feces from infected animals or by contaminated water (1,4,5). In addition to food, E. coli can contaminate water through the presence of infected human or animal feces (6). Many outbreaks of water contamination with E. coli have been reported over the last years. Contamination of drinking water, recreational water and irrigation water are three common causes of outbreaks. The purpose of this paper is to use outbreaks from around the world to identify the reasons why these bodies of water are contaminated and what can be done to prevent contamination.

Contamination of drinking water

For the analysis of the possible causes and ways of prevention contamination of drinking water with E. coli, three outbreaks will be presented.

The first outbreak occurred in May 2000 in Walkerton Ontario where the drinking water supply was contaminated by bacterial pathogens including E. coli O157:H7 causing 7 deaths and making 2300 people ill (7,8). The causes of this outbreak were investigated to find how the public utilities commission (PUC) operators, the Walkerton public utilities commissioners, the Ministry of the Environment (MOE) and the government budget reductions affected the events leading to the outbreak (8). It was reported that a well supplying drinking water was contaminated with E. coli O157:H7 and Campylobacter jejuni because of heavy rainfall that caused a water surface runoff (8). Walkerton is a rural area with many farms, so the manure used on the farms contained the bacteria and the water runoff transported the bacteria into the well (8). The contaminated well was chlorinated but the amount used was less than required because the PUC employees, who have to manually monitor the chlorine level of the well, created false data on their daily operation sheets, which is an habit the employees have repeated for more than 20 years (8). In addition to the daily false entries, other inadequate practices by the PUC included mispresenting the locations where the water samples were taken, inadequate or no chlorination in operating wells, no daily monitoring of chlorine residuals and submitting false annual reports to the MOE (8). These poor practices by PUC are attributed to the lack of training of the two persons in charge of PUC (8). In fact, they are required to have 40h of training each year but they did not have that training (8). As a result, they did not know much about chlorination and the possible health risks related to inadequate treatment and monitoring of drinking water (8). Few years before the outbreak, the MOE found the following deficiencies in the water system: E. coli was found in the treated water of Walkerton, the chlorine residuals were low and the number of samples submitted was too low (8).  In addition, the MOE lacked computerized information system, thus it was impossible for people who were monitoring to have access to the information (8). The MOE reported these problems to the Walkerton public utility commissioners who did not take actions to resolve the problems because of financial issues (8). Therefore, budgetary reductions occurred in the government which caused laboratory privatization and the arrest of testing municipal water samples in government laboratories (8). In summary, inadequate monitoring, human negligence, technology deficits, lack of training, privatization of water testing, and budget restrictions to the MOE caused the Walkerton tragedy (7,8).

In the summer of 1999 in Applecross, a small village of Scotland, an E. coli O157:H7 outbreak occurred (9). All the six cases of infection reported were associated to a campsite region that used untreated drinking water from a private supply that came from a spring (9). The water was monitored by Protective Services officers of the Highland Council who put a boiling water notice one week before the outbreak when the water tested had too much bacterial pathogen (9). The spring was located in an area where sheep and deer could graze freely (9). Some sheep feces were found near the water and then analyzed (9). Results showed that E. coli O157:H7 was found in the feces of the animals suggesting that the infection was caused by the presence of animal feces in water (9). Moreover, only tourists were infected while the permanent residents of the campsite did not get infected showing that risk of infection is increased in travelers and transient populations (9). The fact that the water used in the campsite is untreated is not mentioned to the tourists when they arrive which increases the risk of infection (9).

A larger outbreak of E. coli O157:H7 occurred in the summer of 1998 in Alpine Wyoming (10). In total there were 157 cases of acute gastrointestinal illness and E. coli O157:H7 was found in the feces of 71 of the cases (10). Hemolytic uremic syndrome developed in 4 persons (10). It was noted that no deaths occurred and that everyone recovered from the illness (10). Drinking the municipality water was linked with the development of the illness because people who drank Alpine municipal water were nine times more likely to become sick than people who did not drink the water (10). The contamination of the unchlorinated municipal water happened when the surface water, which contained feces from deer and elk feces infected with E. coli O157:H7, leached into the unconfined aquifer of the municipality (10).  Similarly to the Scotland outbreak, immunity to symptoms occurred because Alpine residents who already have been infected with E. coli O157:H7 did not show symptoms this time.  

The previous outbreaks demonstrated that the main reason why drinking water is contaminated with E. coli O157:H7 is due to the presence of infected animal feces in the water supply. The water can come from a well, a spring or a municipality system and the contamination pattern is still the same: E. coli from feces leached into water. Also, the outbreaks showed the importance of chlorination. In Walkerton chlorination was not well monitored, in Scotland and Alpine the water was unchlorinated, so incorrectly chlorinated or unchlorinated water increases the risk of infection and can cause major outbreaks. It was reported that chlorination of water is one of the main public health measures to assure that both drinking and recreational water do not contain pathogens (11). Results from a study stated that when E. coli O157:H7 strains were exposed to chlorine (1.1mg/L free chlorine and 1.2 mg/L total chlorine) for 1 minute the viable population of the bacteria decreased by four orders of magnitude (11). This shows that E. coli O157:H7 is sensitive and unlikely to survive chlorination, thus chlorination at the levels tested is enough to inactivate the bacterium and prevent contamination of drinking water (11). However, if water is chlorinated, monitoring of the chlorination levels should be done regularly and adequately to ensure that water is well protected because the Walkerton outbreak clearly showed that failure to correctly monitor chlorine levels and human negligence can lead to a major outbreak. Moreover, testing water for the presence of E. coli is also recommended because this bacterium is an indicator of the safety of drinking water (12). The guidelines for Canadian Drinking Water Quality indicate that the presence of E. coli in water represents fecal contamination and the potential presence of microorganisms that can cause gastrointestinal illness (12). Water is considered safe to drink when no E. coli are detected per 100mL of water (12).  In summary, the main source of contamination for drinking water is animal feces and outbreaks related to drinking water can be prevented by chlorination, monitoring the levels of chlorination and testing water quality to ensure safety.