Pathogen disgust sensitivity protects against infection in a high pathogen environment

Abstract

Disgust is hypothesized to be an evolved emotion that functions to regulate the avoidance of pathogen-related stimuli and behaviors. Individuals with higher pathogen disgust sensitivity (PDS) are predicted to be exposed to and thus infected by fewer pathogens, though no studies have tested this directly. Furthermore, PDS is hypothesized to be locally calibrated to the types of pathogens normally encountered and the fitness-related costs and benefits of infection and avoidance. Market integration (the degree of production for and consumption from market-based economies) influences the relative costs/benefits of pathogen exposure and avoidance through sanitation, hygiene, and lifestyle changes, and is thus predicted to affect PDS. Here, we examine the function of PDS in disease avoidance, its environmental calibration, and its socioecological variation by examining associations among PDS, market-related lifestyle factors, and measures of bacterial, viral, and macroparasitic infection at the individual, household, and community levels. Data were collected among 75 participants (ages 5 to 59 y) from 28 households in three Ecuadorian Shuar communities characterized by subsistence-based lifestyles and high pathogen burden, but experiencing rapid market integration. As predicted, we found strong negative associations between PDS and biomarkers of immune response to viral/bacterial infection, and weaker associations between PDS and measures of macroparasite infection, apparently mediated by market integration-related differences. We provide support for the previously untested hypothesis that PDS is negatively associated with infection, and document variation in PDS indicative of calibration to local socioeconomic conditions. More broadly, findings highlight the importance of evolved psychological mechanisms in human health outcomes. Significance Disgust likely evolved to regulate exposure to pathogen-related stimuli and behaviors. One key prediction, that individuals with greater pathogen disgust sensitivity (PDS) will be exposed to fewer pathogens and thus suffer fewer infections, has never been tested directly. To function adaptively, PDS must respond to the local cost/benefit context of avoidance, but this too has been undertested. We provide a test of these predictions among an Indigenous population with notable variation in PDS, infection, and infrastructure. We document predicted negative associations between PDS and pathogen exposure, while illuminating complex, multidirectional relationships among disgust, infection, and environmental variation. Our findings support the hypothesis that disgust functions to regulate pathogen exposure, demonstrating the importance of evolved psychological mechanisms in disease avoidance.