Alterations in the gut resistomes of endangered wild equids associated with anthropogenic activities: Insights for One Health surveillance.

Antibiotic resistance genes (ARGs) are emerging environmental contaminants, but how human-associated management practices are associated with mobile resistomes in endangered wildlife remains poorly resolved. Here, we used fecal metagenomics to compare Przewalski's horses, Mongolian khulans, and domestic horses from Xinjiang, China, including Przewalski's horses from a protected area and a captive-breeding setting under human management. Across 47 fecal metagenomes, we identified 380 ARG subtypes, 23 metal resistance gene (MRG) types, and 26 mobile genetic element (MGE) subtypes. Przewalski's horses and domestic horses carried higher ARG burdens than Mongolian khulans, whereas Mongolian khulans showed a higher MRG burden. Within Przewalski's horses, captive individuals had higher ARG and MGE loads than protected-area individuals, with enrichment of tet(W), lnu(C), vanYG1, transposase genes, and IS91. Co-occurrence networks and structural equation modeling indicated that the captive management setting was positively associated with IS91, which in turn was linked to ARG enrichment and ARG-MRG co-occurrence. Genome-resolved analysis recovered 590 medium- to high-quality metagenome-assembled genomes (MAGs) and revealed that MAGs co-carrying ARGs, MRGs, and MGEs were predominantly assigned to anaerobic gut genera, including Prevotella, Alloprevotella, Cryptobacteroides, and Limivicinus. These findings suggest that human-associated wildlife habitats are associated with increased mobility potential of gut resistomes through the enrichment of MGEs and resistance carrying host bacteria. Endangered equids may therefore act as sentinels for AMR reservoirs at wildlife-human-environment interfaces, supporting ARG and MGE monitoring in protected-area and captive management programs.