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Long-Term Goal 4-03: Research Description
Back to Long-Term Goal 4 (LTG 4):
Research Descriptions and Posters
Title: Salivary antibody as a novel indicator of incident waterborne infections. Can it help to evaluate the beneficial health effect of improvements in water treatment?
Presenters: Andrey Egorov (NCEA), Tim Wade (NHEERL), Shay Fout (NERL)
Contributors: Shannon Hunt (NCEA), Kevin Reilly (Region 1)
Science Questions:
- Is salivary antibody a feasible and cost-effective bioindicator of incident infections in longitudinal studies of waterborne infections?
- Can linkages be made between risk mitigation actions that bring drinking water treatment plants into compliance with drinking water regulations and reduction in the incidence of endemic waterborne infections?
- Is there a reduction in the incidence of selected common waterborne infections in a selected community following a regulatory-driven improvement in treatment of water derived from a microbiologically challenged river?
The Research:
Waterborne infections can be caused by a variety of viral, bacterial and protozoan pathogens. The protozoan parasite Cryptosporidium is of major concern for water utilities which use unprotected surface water sources due to its extreme resistance to chlorination. Enteric viruses, such as noroviruses and rotaviruses, are also relatively resistant to disinfection. Recent regulatory actions, such as the Long Term 2 Enhanced Surface Water Treatment Rule (LT2), were developed to reduce the incidence of waterborne diseases associated with Cryptosporidium and other microorganisms in drinking water. Characterizing the incidence of waterborne infections and assessing reductions in these infections due to better water treatment remain a challenge for a number of reasons: 1) most cases of gastroenteritis are self-treated, often using non-prescription medication that does not involve contact with a physician or health-care provider; 2) even when medical care is provided, fecal samples are rarely tested for Cryptosporidium and enteric viruses; 3) these infections can be acquired from sources other than drinking water; 4) occurrence data on these pathogens in raw and treated water are limited; and 5) it can be difficult to demonstrate a statistical association (and even more difficult to show causality) between water quality and endemic infections in non-outbreak settings. Epidemiological studies that include collection and analysis of fecal samples, or testing of blood samples for antibodies to these pathogens have proven to be expensive, difficult to organize and typically exclude children from aspects of the study that require serum samples.
Pathogen-specific antibodies in saliva can be used as a bioindicator of recent or ongoing infection. Because collection of saliva is easy and painless, immunoassays designed to detect antibodies in oral fluid can be used in prospective studies, which involve collection of multiple samples. A steep increase in specific salivary antibody between consecutive samples (immunoconversion) serves as a bioindicator of incident infections.
This study is a collaboration between ORD's Labs and Centers, Region 1, and the Office of Water. It is designed to compare incidence rates of potentially waterborne infections in Lawrence, MA before and after this city replaced an outdated water treatment plant (built in 1938) with a new state-of-the-art plant. The new plant uses primary disinfection with chlorine dioxide and irradiation with ultraviolet light, and secondary disinfection with chlorine. Each phase of this study (before and after new treatment) enrolls approximately 400 local families with children under 12 years of age. Data collection involves monthly saliva sampling and surveys of gastrointestinal symptoms and tap water consumption.
Multiplex microbead suspension immunoassays based on Luminex technology were developed for measurements of salivary IgA and IgG responses to Cryptosporidium spp., Norwalk virus, norovirus VA387, rotaviruses, Toxoplasma gondii, and Helicobacter pylori. Saliva and serum samples collected from 25 EPA volunteers were used to optimize and validate this immunoassay. During the first phase (before new treatment) of the study, more than 5000 saliva samples were collected from 1398 individuals from June through December 2006. Saliva samples from the first phase are presently being analyzed. Immunoconversions to noroviruses have been detected in individuals who reported diarrhea and vomiting symptoms typical of norovirus infections. The new treatment plant became operational in March 2007. Analysis of drinking water turbidity data has confirmed a significant reduction in turbidity following the initiation of water treatment from the new treatment plant. Raw and treated water quality monitoring also demonstrated that removal of waterborne pathogens and indicator organisms improved at the new plant. In June 2008, field data collection was initiated for the second phase (after completion of the new treatment plant). Recruitment has been completed at the beginning of October; follow-up was ongoing in November 2008.
Impact and Outcomes:
- Development of a salivary antibody bioindicator that can be used for detection of incident infections with pathogens which can be transmitted through drinking water.
- Demonstration of the application of this non-invasive biomarker to link Agency regulations designed to improve microbiological water quality with improvements in public health.
- Potential for application to other studies of infections associated with drinking water and other media such as studies of illnesses resulting from recreational water contacts at public beaches.
Key Products:
Hunt SM, Fout GS, Chen I, Wade TJ, Egorov AI. Application of a multiplex immunoassay for detection of salivary antibody responses to selected potentially waterborne pathogens. 20th Annual Conference of the International Society for Environmental Epidemiology. October 2008, Pasadena, CA.
Fout GS, Brinkman NE, Karim MR, Rhodes ER, Egorov A, Hunt SM. Methods for Measuring Occurrence and Exposure from Viruses in Drinking and Recreational Waters. "Future Direction of Improvement in Drinking Water Safety", Incheon, Korea, March 2008.
Egorov A, Wade T, Fout GS. Salivary antibody responses as an indicator of waterborne infections: pilot community study before and after installation of UV treatment. "Research Approaches to Assessing Public Health Impacts of Risk Management Decisions", US EPA, RTP, January 2008.
Hunt SM, Wade TJ, Fout GS, Egorov AI. Salivary antibody responses as an indicator of waterborne infections: pilot community study before and after installation of UV treatment. Workshop on Public Health Applications of Human Biomonitoring. USEPA and International Council of Chemical Associations, September 2007, Research Triangle Park, NC.
Hunt SM, Fout GS, Rothermich M, Wade TJ, Egorov AI. Evaluation of salivary antibody immunoassay for detection of Cryptosporidium infections. Annual meeting of the American Society of Parasitologists. June 2007, Merida, Yucatan, Mexico.
Dingwall M, Wool M, Jasim-Hanif S, Wade TJ, Egorov AI, Williams A. Recruitment and Retention for a Hispanic Population: Results from a Community Health Study. American Association for Public Opinion Research, Annual Conference. May 2007, Anaheim, CA.