Seasonal Trends in Water Contamination and Cryptosporidium Infections

This study is part of an ongoing effort to determine the prevalence of the contamination of well water by septic tank contents, and investigate the public health impacts of these interacting systems. Methods: A prospective cohort of 59 Hispanic and non-Hispanic adults living in and around Albuquerque, New Mexico was followed for 13 months. Well-water samples were collected every two months and tested for indicators of contamination (total coliforms, E. coli, Enterococci and somatic coliphage). Blood samples and questionnaire data were collected every three months. Blood was tested for antibodies to Cryptosporidium parvum. Analysis was performed to determine the characteristics of cohort participants with high levels of Cryptosporidium antibodies and well-water contamination. Results: Individuals with a positive total coliform well-water test had an increased prevalence of having Cryptosporidium antibodies ≥75% of a positive control (OR 3.4, 95% confidence interval: 1.1-10.8). A positive E. coli well-water test also suggested an increased prevalence of having Cryptosporidium antibodies ≥75% of a positive control. (OR 2.9, 95% confidence interval: .96-8.7). The percentage of participants giving different answers for risk factor exposures on repeated questionnaires ranged from 2% up to 79%. Answers to frequency of diarrheal and gastro-intestinal illnesses changed in 36% and 41% of the repeated questionnaires, respectively. For the remainder of the twenty risk factors, the answers changed more than 25% for nine of the variables. Conclusions: Individuals with contaminated water tests had increased odds of Cryptosporidium infection. Positive water tests are common and seasonal. Risk factor data changed substantially over a 13 month period.