Tracking pathogens with eDNA in natural areas: how environmental gradients shape surveillance strategies

The wildlife-livestock-environment interface is a complex system with implications for biodiversity and diseases. Environmental nucleic acid detection (ENAD) is a non-invasive method for monitoring pathogens via DNA/RNA. However, how environmental variables influence ENAD remains poorly explored in heterogeneous geographic contexts.In this study, 18 sites were evaluated in Iberian Peninsula, collecting 10 surface sponge samples per site and a total of 146 environmental fecal samples. Differences in pathogen ENAD were assessed among sponge sampling methods and between sponge and fecal samples. The relationship between ENAD results and environmental, mammal community and wildlife health variables was investigated.The results show that environmental characteristics influence pathogen ENAD at larger geographic scales, with greater pathogen diversity and richness observed at higher latitudes. Most markers found in feces were also detectable in surface sponges. Combining different sponge sampling methodologies provides the best overall coverage of detectable pathogen markers. A predictive map linking pathogen ENAD in sponges to environmental factors was developed.