Are cases of enteric disease due to Salmonella, Campylobacter, Giardia, and Cryptosporidium associated with well water?

BACKGROUND: Campylobacter, non-typhoidal Salmonella, Shigella, Cryptosporidium, and Giardia are responsible for ~1 million domestically acquired waterborne illnesses annually in the United States. The contribution of private well water and underlying geology to these infections has been underexplored. The objectives of this research were to (1) determine whether enteric disease cases in Pennsylvania cluster in time and space; and (2) determine whether enteric disease cases are associated with private well water and karst geology.

METHODS: Confirmed cases of Campylobacter, non-typhoidal Salmonella, Cryptosporidium, and Giardia from 2010 to 2019 in Pennsylvania were analyzed. Spatial clusters were identified using a Poisson-based spatial scan statistic (SaTScan), and temporal patterns were examined using the R package Model Temporal Trends. Zero-inflated negative binomial model regression with county-level random intercepts examined associations between disease incidence, private well usage, and karst geology.

RESULTS: All four pathogens had significant clusters of illness in time and space. Cryptosporidium, Giardia, and Campylobacter cases were significantly associated with areas served by private wells ( P < 0.05; P < 0.001), and cases of Cryptosporidium and Campylobacter were associated with karst geology ( P < 0.01).

CONCLUSIONS: This novel investigation adds to a growing body of evidence that private well water is a risk factor for enteric disease. Public health interventions should target the management of private well water to reduce the burden of disease globally, particularly in communities not serviced by public water supplies.