Sludge Watch ==> The dark side of the e coli outbreak - renal failure even if you didn't know you were sick

[Maureen Reilly]

The Dark Side of an Ecoli 0157H7 outbreak - renal failure 

The people who have been diagnosed ill in this outbreak are not the only ones who may suffer permanent damage to their kidney functioning from this outbreak.
Here are the lessons on health problems following the Walkerton outbreak in Ontario, Canada.


After the whole town of Walkerton Ontario was exposed to Ecoli 0157 and Campylobactor jejeuni there was a follow up clinic.  The clinic tested townspeople who 
were diagnosed with an infection during the outbreak, had only transitory symptoms, and were asymptomatic.  Here is a brief summary.

Note the very high high rates of diminished renal functioning even in the undiagnosed and asymptomatic group.  When, in this spinach Ecoli outbreak we see
185 people infected...there are likely 2000 more who don't know it...and a percentage of those people may be losing  kidney function.  As to the hypertension...well
who wouldn't be hypertensive if you lived in a town whose name is synonymous with death and disease?  Where so many live with the long term effects of the
water contamination.  

What can be done about the problems faced by the victims of Ecoli O157 who don't know they got it?  How will they know to check for renal function?  
 I don't know what to suggest, except that family members and those dining with victims need to get checked.

  It speaks to the need to stop intensive livestock operations (CAFOs) from generating Ecoli 0157 by changing cattle
feed regimes to not include the grain fed finishing feed lot that promotes the Ecoli0157 pathogen.  

And we need better laws (not guidelines) about waste management, water quality, and food safety.

Maureen Reilly
Sludgewatch
416 922 4099

http://www.waterquality.crc.org.au/hsarch/hs38j.htm
Risk of hypertension and reduced kidney function after acute gastroenteritis from bacteria-contaminated drinking water. 
Garg AX, Moist L, Matsell, D et al. (2005) Canadian Medical Association Journal, 173 (May 27, early release online). 
In May 2000, the municipal water supply in Walkerton, Ontario was contaminated with Escherichia. coli 0157:H7 and Campylobacter species, leading to a large waterborne outbreak. There were over 2300 people affected by acute gastroenteritis and 6 deaths were attributed to the outbreak. This paper describes a followup study of adults affected by the outbreak to determine whether bacterial gastroenteritis may lead to long-term health problems. After the outbreak people who had either lived in the Walkerton area or who had consumed municipal water at the time of the outbreak were invited to participate in a follow up study to evaluate the long term risk of hypertension and reduced kidney function and albuminuria.

There were 1958 adults who participated in the study, and virtually all (99.3%) reported drinking contaminated water during the outbreak. These participants had no known history of diabetes, hypertension, kidney disease or chronic gastroenteritis symptoms prior to the outbreak. Among the group, there were 675 participants who had been asymptomatic during the outbreak, 909 who had moderate symptoms of acute self-limiting gastroenteritis and 374 who had severe symptoms and needed medical attention. Gastroenteritis symptoms were classified according to medical records made at the time of the outbreak in order to avoid recall bias.

Participants were examined at 2, 3 and 4 years after the outbreak. The primary outcome examined was hypertension (high blood pressure). Kidney function was also assessed by estimating the glomerular filtration rate and measuring levels of albumin in the urine.

The demographic characteristics and health status of the three groups were similar before the outbreak, except that smoking was significantly less common among those who remained asymptomatic for gastroenteritis (p=0.003). There were 492 participants with a diagnosis of hypertension after the outbreak after an average of 3.7 years of follow up. Of those participants who were asymptomatic during the outbreak, 27% were diagnosed with hypertension, of those with moderate gastroenteritis, 32.3% were diagnosed with hypertension, and of those who had severe gastroenteritis, 35.9% were diagnosed with hypertension. This was a significant trend (p = 0.009). When those with moderate and severe gastroenteritis were compared with asymptomatic participants an adjusted relative risk of a new diagnosis of hypertension was found to be 1.15 (95% CI 0.97-1.35) and 1.28 (95% CI 1.04-1.56) respectively. In order to exclude the possibility that some people may have had undiagnosed hypertension prior to the outbreak, the analysis was repeated including only people who had normal blood pressure at the first study visit (n=1049), and a weaker but still significant trend was found (p=0.04).

A total of 38 participants were found to have reduced kidney function over 3.7 years of follow up. Reduced kidney function was defined as having a glomerular filtration rate below 60 mL/min per 1.73 m2. Of those participants who were asymptomatic, 2.2% had reduced kidney function, of those with moderate gastroenteritis, 3.9% had reduced kidney function, and of those with severe gastroenteritis, 6.9% had reduced kidney function (p= 0.03). There were no associations found for albuminuria. 

This study found that those with symptomatic bacterial gastroenteritis from contaminated drinking water were more likely to have newly diagnosed hypertension and reduced renal function during the 3.7 years of follow up after infection. Therefore maintaining safe drinking water is again shown to be important as the health consequences of an outbreak may extend beyond the initial period of illness. 

Comment The authors note that for most participants no information was available on which pathogen they had been infected by. Among those in the study with severe gastroenteritis symptoms 40% had a stool culture performed during the outbreak, with 14% diagnosed with E.coli O157:H7, 17% with Campylobacter and 2% with both pathogens. This ratio is somewhat different to that found in the outbreak investigation where E.coli was more common than Campylobacter (167 people with confirmed E.coli infections vs 116 with confirmed Campylobacter). The Shiga toxin produced by E. coli O157:H7 is known to attack the kidney, and kidney damage may lead to an increase in blood pressure. However Campylobacter infection is not currently known to produce hypertension as a long term after-effect. The authors note that the psychological stress associated with illness may also be a contributor to hypertension.
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