Citation:

Egorov, A., R. Converse, S. Griffin, R. Bonasso, L. Wickersham, E. Klein, J. Kobylanski, R. Ritter, J. Styles, H. Ward, E. Sams, E. Hudgens, A. Dufour, AND T. Wade. Recreational water exposure and waterborne infections in a prospective salivary antibody study at a Lake Michigan beach. Scientific Reports. Nature Publishing Group, London, Uk, 11:20540, (2021). https://doi.org/10.1038/s41598-021-00059-2

Impact/Purpose:

This manuscript presents results of a prospective epidemiological study in recreational water users at a Great Lakes beach. This study applied a multiplexed, non-invasive salivary antibody assay developed at EPA to detect incident infections with noroviruses and Cryptosporidium spp. after an episode of recreational water exposure, and to link infections with intensity of water contacts, and with gastrointestinal symptoms. These results contribute to the body of epidemiological evidence linking recreational water use with waterborne infections under the SSWR research area.  

Description:

Background. Seroconversion to a pathogen-specific antibody is a marker of an incident infection with a specific pathogen. While self-reported symptoms can be affected by reporting bias, seroconversion is likely to be free of this bias as it is based on objective measurements of antibody response. Non-invasive salivary antibody tests can be used instead of serum tests to detect seroconversions in prospective studies including sampling by mail. This non-invasive method can enable population studies of drinking water-borne and recreational water-borne infections in order to characterize their risk factors. Methods. Individuals and families were recruited at a Lake Michigan beach in Wisconsin in August 2011. Data on recreational water exposure and baseline saliva samples (S1) were collected at recruitment. Follow-up data on gastroenteritis symptoms were collected via a telephone interview approximately ten days post recruitment. Follow-up saliva samples were self-collected approximately two weeks (S2) and 30-40 days post-recruitment (S3) and mailed to the study laboratory. Samples were analyzed for immunoglobulin (Ig) G responses to recombinant antigens of three noroviruses and Cryptosporidium, as well as protein purification tags as internal controls using an in-house multiplex suspension immunoassay on the Luminex platform. Responses were defined as ratios of antibody reactivities with a target protein and its purification tag. Seroconversions were defined as at least four-fold and three-fold increases in responses in S2 and S3 samples compared to S1, respectively. In addition, an S2 response had to be above the upper 90% one-sided prediction limit of a corresponding spline function of age.   Results. Among 872 study participants, there were seven (0.8%) individuals with seroconversions, including six individuals with seroconversions to noroviruses. Among 176 (20%) individuals who reported swallowing lake water, there were six (3.4%) seroconversions compared to one (0.14%) seroconversion among the remaining 696 individuals: the crude and age-standardized risk differences per 1,000 beachgoers were 32.7 (95% confidence limits 5.7; 59.6) and 94.8 (4.6; 276), respectively. The age-adjusted odds ratio of seroconversion in those who swallowed water vs. all others was 49.5 (4.5; 549), p=0.001. Individuals with a norovirus seroconversion were more likely to experience vomiting or nausea symptoms within four days of the index beach visit than non-converters with 34 (3.4, 350), p=0.003, and 11 (1.2, 96), p=0.04, odds ratios, respectively.     Conclusions. This study contributed further evidence that recreational water exposure is associated with symptomatic and asymptomatic waterborne infections, and that salivary antibody assays can be used in epidemiological surveys of norovirus and Cryptosporidium infections.

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