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PAIRED-CITY STUDY TO DETERMINE THE CONTRIBUTION OF SOURCE WATER TYPE TO THE ENDEMIC LEVEL OF MICROBIAL DISEASE
Citation:
Frost, F. J., T. Kunde, L. Harter, T. Muller, G. Craun, AND R L. Calderon. PAIRED-CITY STUDY TO DETERMINE THE CONTRIBUTION OF SOURCE WATER TYPE TO THE ENDEMIC LEVEL OF MICROBIAL DISEASE. Presented at International Society for Environmental Epidemiology, Perth, Australia, September 26, 2003.
Description:
Paired-City Study to Determine the Contribution of Source Water Type to the Endemic Level of Microbial Disease
F Frost PhD, T Kunde MPH, L Harter PhD, T Muller MS, GF Craun PE MPH, RL Calderon MPH PhD
ABSTRACT
Context: The effectiveness of current drinking water regulations for the prevention of endemic gastrointestinal illness (GI) is being evaluated in a series of community intervention studies in the United States. The U.S. Environmental Protection Agency recently established regulations that require increased treatment of surface waters and ground water under the direct influence of surface waters. We identified communities that, as the result of these drinking water regulations, were planning to make changes in their water treatment processes and replace disinfection as the only treatment of surface water with filtration and disinfection. The rate of GI in the community would be evaluated before and after addition of filtration. A geographically co-located city would also be studied to adjust for community variability in GI. This study reports on the second of these community intervention studies.
Methods:
Design. A longitudinal cohort was followed prospectively for six months (July 2000 - Nov 2000) before filtration and six months (July 2001 - Nov 2001) after filtration. Setting. Households in two northwestern communities, one of which was upgrading drinking water treatment by adding filtration as a treatment for surface water. Households in the paired community used disinfected groundwater. Patients. Households with adults over 65 and families with a child between 2 and 10 years of age were recruited in the two cities. Main Outcome Measures. Households were asked to keep a diary of GI frequency. A subset of families were asked to supply blood samples for a serosurvey. Outcomes were both illness as measured using "highly credible gastrointestinal illness" (HCGI) and seropositivity for Cryptosporidium antibodies.
Results: The serological responses between the cities were not significantly different in the phase prior to filtration. During the second six months, serological responses differed significantly for participants in the two cities. In the filtered-water community, the prevalence of seropositivity for Cryptosporidium antibodies decreased after filtration and was lower than in the comparison community. Significant protective relationships for diarrheal and other GI events were observed for serological responses to Cryptosporidium.
Conclusion: Water filtration appeared to reduce Cryptosporidium infection. Serological evidence of prior Cryptosporidium infection is predictive of a reduced occurrence of gastrointestinal and diarrheal illness. The overall assessment of HCGI illness as the result of improved water treatment is pending.