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Waterborne cryptosporidiosis associated with a borehole supply
Insights
A 1993 cryptosporidiosis outbreak in one district affected 64 people, primarily linked to a town's public water supply. Consumption of this water significantly increased illness risk, indicating a potential waterborne transmission route.
Area of Science:
- Public Health
- Epidemiology
- Environmental Health
Background:
- Cryptosporidiosis outbreaks pose significant public health challenges.
- Waterborne transmission is a known route for parasitic infections like cryptosporidiosis.
Purpose of the Study:
- To investigate the cause and transmission of a cryptosporidiosis outbreak.
- To identify the source of infection and assess risk factors.
Main Methods:
- Case-control study design.
- Epidemiological investigation of diagnosed cases.
- Water quality testing for oocysts.
Main Results:
- 64 cases of cryptosporidiosis diagnosed between April and May 1993.
- 35 primary cases clustered in an area served by a specific public water supply.
- Households using the affected supply were 15 times more likely to be ill; a dose-response relationship was observed.
Conclusions:
- The public water supply was strongly implicated as the source of the cryptosporidiosis outbreak.
- Despite low oocyst detection weeks later, the likely mechanism of contamination remains unclear.
- Public health interventions are crucial for preventing future waterborne disease transmission.
Abstract:
From 1 April to 31 May 1993, 64 cases of cryptosporidiosis were diagnosed within one district health authority. Forty were classified as primary cases, 35 of whom were clustered in an area supplied by a discrete public water supply that supplied the majority of homes in a large town. Most of the water in this supply is abstracted from boreholes and some is filtered before distribution. Households that received mains water from this supply were 15 times more likely to be affected than households nearby that received water from other sources. A case control study demonstrated a dose response relationship between consumption of water obtained from the town supply and risk of illness. Very low concentrations of cryptosporidial oocysts were detected in the water supply on four occasions several weeks after the outbreak. Environmental investigation failed to reveal a likely mechanism for contamination of the water supply.