Cryptosporidiosis and Water Filtration in Scotland
Author Information
Author(s): Kevin G.J. Pollock, David Young, Huw V. Smith, Colin N. Ramsay
Primary Institution: Health Protection Scotland
Hypothesis
If a proportion of cases of illness were attributable to drinking unfiltered Loch Lomond water, then illness incidence should be reduced after the introduction of enhanced water treatment.
Conclusion
Upgrading water treatment, particularly introducing coagulation and rapid gravity filtration systems, can substantially reduce the numbers of cryptosporidiosis cases.
Supporting Evidence
- Before filtration, the incidence of cryptosporidiosis was 12.8 cases per 100,000 population in Loch Lomond.
- After filtration, the incidence dropped to 6.5 cases per 100,000 in Loch Lomond.
- Statistical analysis showed a significant association between water source and incidence of cryptosporidiosis.
Takeaway
Drinking unfiltered water from Loch Lomond made people sick, but after they started filtering the water, fewer people got sick.
Methodology
The study was a retrospective cohort analysis of microbiologically confirmed cases of cryptosporidiosis among residents of central Scotland from 1997 to 2003.
Potential Biases
The study may be confounded by other water sources and environmental factors affecting cryptosporidiosis incidence.
Limitations
The study was based on the home location of case-patients and the water supply to that location, limiting individual exposure data.
Participant Demographics
Most case-patients were children aged 5-14 years, with a significant portion being male.
Statistical Information
P-Value
<0.001
Confidence Interval
95% CI 2.8–4.4
Statistical Significance
p<0.001
Digital Object Identifier (DOI)
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