Avian influenza antibody prevalence increases with mercury contamination in wild waterfowl

Abstract

Environmental contamination is widespread and can negatively impact wildlife health. Some contaminants, including heavy metals, have immunosuppressive effects, but prior studies have rarely measured contamination and disease simultaneously, which limits our understanding of how contaminants and pathogens interact to influence wildlife health. Here, we measured mercury concentrations, influenza infection, influenza antibodies and body condition in 749 individuals from 11 species of wild ducks overwintering in California. We found that the odds of prior influenza infection increased more than fivefold across the observed range of blood mercury concentrations, while accounting for species, age, sex and date. Influenza infection prevalence was also higher in species with higher average mercury concentrations. We detected no relationship between influenza infection and body fat content. This positive relationship between influenza prevalence and mercury concentrations in migratory waterfowl suggests that immunotoxic effects of mercury contamination could promote the spread of avian influenza along migratory flyways, especially if influenza has minimal effects on bird health and mobility. More generally, these results show that the effects of environmental contamination could extend beyond the geographical area of contamination itself by altering the prevalence of infectious diseases in highly mobile hosts.

Waterfowl recently infected with low pathogenic avian influenza exhibit reduced local movement and delayed migration

“…Finally, most birds were sampled weeks or months before migration, leaving their infection statuses during migration unknown. Longitudinal studies that resample individuals (Tolf et al, 2013; Trovão et al, 2021) could help clarify the causal nature of these relationships as well as how infection interacts with stressors such as habitat availability and environmental contamination (Teitelbaum, Ackerman, et al, 2022). Regardless of the mechanism driving infection–movement relationships, these associations can alter the expected dynamics of infection prevalence by affecting contact patterns between individuals, environmental exposure, and the role of birds as dispersal vectors.…”

Mercury Bioaccumulation and Cortisol Interact to Influence Endocrine and Immune Biomarkers in a Free-Ranging Marine Mammal

“…These decreases suggest possible immunosuppressive effects of mercury within both the adaptive and innate immune systems, which can increase the susceptibility of seals with higher muscle mercury concentrations to pathogens. As an example, the likelihood of influenza infection increased with increasing mercury contamination in wild waterfowl and mercury had immunosuppressive effects in multiple other bird species. ,,, In vitro experiments with animal cells provide additional examples of how elements of both the adaptive and innate immune systems may be suppressed in response to mercury. ,,,, …”

Interactive effects of rising temperatures and urbanisation on birds across different climate zones: A mechanistic perspective

“…Thus, higher environmental temperatures make the risks of poisoning more acute (Dearing, 2013), especially in urban areas. Furthermore, recent work suggests higher pollutant loads may make birds less resilient to pathogens (Teitelbaum et al, 2022),…”