Salivary Antibodies against Multiple Environmental Pathogens Found in Individuals Recreating at an Iowa Beach

Abstract

Detecting environmental exposures and mitigating their impacts are growing global public health challenges. Antibody tests show great promise and have emerged as fundamental tools for large-scale exposure studies. Here, we apply, demonstrate and validate the utility of a salivary antibody multiplex immunoassay in measuring antibody prevalence and immunoconversions to six pathogens commonly found in the environment. The study aimed to assess waterborne infections in consenting beachgoers recreating at an Iowa riverine beach by measuring immunoglobulin G (IgG) antibodies against select pathogens in serially collected saliva samples. Results showed that nearly 80% of beachgoers had prior exposures to at least one of the targeted pathogens at the beginning of the study. Most of these exposures were to norovirus GI.1 (59.41%), norovirus GII.4 (58.79%) and Toxoplasma gondii (22.80%) and over half (56.28%) of beachgoers had evidence of previous exposure to multiple pathogens. Of individuals who returned samples for each collection period, 6.11% immunoconverted to one or more pathogens, largely to noroviruses (GI.1: 3.82% and GII.4: 2.29%) and T. gondii (1.53%). Outcomes of this effort illustrate that the multiplex immunoassay presented here serves as an effective tool for evaluating health risks by providing valuable information on the occurrence of known and emerging pathogens in population surveillance studies.

Keywords: Buffalo Shores Beach; Iowa; Luminex; coinfection; environmental pathogens; immunoassay; immunoconversion; immunoprevalence; incident infection; multiplex; population surveillance; public health; recreational beach; saliva; waterborne.

Figure 1

Maps of (A) the United States displaying the study area on the eastern border of Iowa. (B) The study area (lower left in dark blue) is along the Mississippi River downstream from Davenport, Iowa, and multiple wastewater treatment plants (WWTP). (C) A snapshot of the Buffalo Shores Beach recreational area.

Figure 2

Immunoprevalence for targeted pathogens. (A) Median Fluorescence Intensity units (MFI) scatterplot showing all S1 samples with the cutoff (red line: 739.02 MFI) distinguishing positive (above) and negative (below) samples. (B) Immunoprevalence heatmap displaying the positive samples denoted by black lines.

Figure 3

Immunopositivity summary: exposure status of the individuals who provided a saliva sample for each collection period (S1–S3). Upper panel: black lines represent the samples positive (MFI ≥ cutoff) for the targeted pathogens. Lower panel: % immunopositivity for the targeted pathogens.

Figure 4

Immunoconversion summary denoting the number of immunoconversions and co-immunoconversions to the pathogens under study. Note Tg: T. gondii; GI.1: norovirus GI.1; GII.4: norovirus GII.4; HAV: hepatitis A virus and Hp: H. pylori.

Figure 5

MFI curves for the pathogens under study. Plots showing IgG in MFI from S1 to S3 for immunoconversions. Red dashed line = cutoff (739.02 MFI).