Supplementary Tables for Ecosphere Submission

Wildlife diseases are a major threat to biodiversity. In Australia, the iconic koala is experiencing population decline due to chlamydial disease (mostly from Chlamydia pecorum). Determining the factors that contribute to infection and disease outcomes is crucial to inform koala conservation - and thus is expected to be widely researched. In this systematic review, we collate 80 papers which examine relationships between epidemiological factors and Chlamydia in koalas. Studies measure Chlamydia using differing metrics. While the majority include both infection and disease status (N = 49), diagnosis of Chlamydia is frequently inferred from disease observation without molecular confirmation (N = 23). Results of this review are presented as per the triad model of epidemiology, delineated into host, environmental, and pathogen components. Overall, we undercover a lack of research encompassing factors from all three model components (N = 5), compounded by a reduction in number of research outputs in the last four years. Factors relating to host and environmental components were far more represented than pathogen factors, both in their number of studies and associated koala sample size. Even where the same factors were present across studies, their effect on Chlamydia was incongruent, with opposing results presented within and between koala populations across studies. Stronger evidence was found for influences on Chlamydia from host and pathogen genetics, with additional impacts from climatic factors. Replicating research geographically, precisely defining metrics, and including factors across all components of the epidemiology triad are still required to understand and combat the threat of chlamydial disease in koalas.