Microbial dysbiosis and its implications for disease in a genetically depauperate species

ABSTRACT THE host-associated microbiome is increasingly recognized as a critical player in health and immunity. When commensal microbial communities are disrupted, dysbiosis can contribute to disease pathogenesis and severity. Santa Catalina Island foxes ( Urocyon littoralis catalinae ) present an ideal case study for examining dysbiosis in wildlife due to their depauperate genomic structure and extremely high prevalence of ear canal tumors. Although the precise cause is yet unknown, infection with ear mites ( Otodectes cynotis ) has been linked to chronic inflammation, which is associated with abnormal cell growth and tumor development. Given the paucity of genomic variation in these foxes, other dimensions of molecular diversity, such as commensal microbes, may be critical to host response and adaptation. We therefore characterized the host-associated microbiome across six body sites of Santa Catalina Island foxes, and performed differential abundance testing between healthy and mite-infected ear canals. We found that mite infection was significantly associated with reduced microbial diversity and evenness, with the opportunistic pathogen Staphylococcus pseudintermedius dominating the ear canal community. These results suggest that secondary bacterial infection may contribute to the sustained inflammation associated with tumor development. Uncovering high abundance of S. pseudintermedius provides critical insight into the pathogenesis of this complex system, as the emergence of antibiotic resistant strains remains a concern of the medical, veterinary, and conservation communities. Through use of culture-independent sequencing techniques, this study contributes to the broader effort of applying a more inclusive understanding of molecular diversity to questions within wildlife disease ecology.