Recreational water exposure is associated with asymptomatic and symptomatic salivary antibody immunoconversions to waterborne pathogens

Non-invasive salivary antibody tests can be used to detect symptomatic and asymptomatic waterborne infections in prospective studies. Immunoconversion as a marker of infection is free of reporting bias potentially affecting self-reported symptoms. Families with children were recruited at a Lake Michigan beach in Wisconsin in summer 2011. Data on recreational water contacts and baseline saliva samples (S1) were collected at recruitment. Follow-up saliva samples were self-collected at 10-14 days (S2) and 30-40 days post-recruitment (S3). Samples were analyzed for IgG responses to recombinant antigens of six noroviruses and Cryptosporidium, and control antigens using an in-house multiplex suspension immunoassay. Immunoconversions were defined as at least four-fold and three-fold increases in antibody responses in S2 and S3 samples compared to S1, with S2 responses to noroviruses and Cryptosporidium above the upper 80% or 90% corresponding prediction limits of spline function on age, respectively. Among 875 study participants, 8 (0.9%) individuals experienced immunoconversions including 7 immunoconversions to noroviruses. Swallowing lake water during the baseline beach visit (176 individuals with 5 (2.8%) immunoconversions) was associated with 13.7 (95% confidence limits 2.4; 80.0), p=0.004, age-adjusted odds ratio (aOR) of immunoconversion to noroviruses or Cryptosporidium. In turn, individuals with norovirus immunoconversion had 33.7 (3.2; 355), p=0.003, aOR of vomiting, and 8.8 (1.0; 77.3), p=0.05, aOR of experiencing nausea symptoms within four days of the baseline survey compared to non-converters. This study provided further evidence that recreational water exposure is associated with symptomatic and asymptomatic waterborne infections. This abstract does not represent EPA policy.

Impact/Purpose

This abstract presents preliminary results of an epidemiological study in beachgoers quantifying the risk of waterborne infections after contacts with fecally contaminated water. This study used a novel non-invasive multiplex salivary antibody method developed by EPA to detect both symptomatic and asymptomatic infections with specific pathogens including various noroviruses and Cryptosporidium. An in-house multiplex suspension immunoassay was used to detect immunoconversions or steep increases in specific salivary antibody responses in follow-up samples compared to baseline. This is the first salivary antibody study in beachgoers that demonstrated both a strong association between accidental water ingestion and immunoconversion, and between immunoconversion to noroviruses and acute symptoms characteristic of norovirus infection. These results are important because salivary antibody immunoconversion is an objective outcome measure which is free of reporting bias that may affect studies using self-reported symptoms as an outcome.

Citation

Egorov, A., S. Griffin, R. Converse, L. Wickersham, E. Klein, R. Bonasso, J. Styles, J. Kobylanski, E. Sams, E. Hudgens, A. Dufour, AND Tim Wade. Recreational water exposure is associated with asymptomatic and symptomatic salivary antibody immunoconversions to waterborne pathogens. National Recreational Water Quality Workshop, Chicago, IL, April 06 - 08, 2021.