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