Urban koala-disease dynamics: A zoo-based case study in disease monitoring and welfare

Thesis Abstract

Urban koala-disease dynamics within metropolitan zoological collections present a pressing welfare and conservation concern due to increasing urbanization, human-wildlife interfaces, and the potential spillover of infectious agents between captive and adjacent wild populations. This study addresses the gap in understanding how managed koala populations in zoos respond to urban stressors, how disease surveillance can be integrated with welfare indicators, and how such dynamics influence comparative health outcomes across age, sex, and enclosure types. The aim is to elucidate disease dynamics, welfare status, and the interplay between environmental and management factors that shape koala health in an urban zoo setting. Specific objectives include (1) characterizing the prevalence and incidence of key koala diseases (including Chlamydia pecorum infection, koala retrovirus exposure, and opportunistic respiratory pathogens) over a three-year period (2019–2021) using routine veterinary records and targeted screening; (2) evaluating welfare indicators—behavioral stress proxies, fecal cortisol metabolites, body condition scores, and enclosure enrichment metrics—and their associations with disease markers; (3) identifying environmental and management predictors (temperature-humidity indices, noise levels, visitor density, diet quality, and enrichment frequency) of disease risk and welfare outcomes; (4) developing a predictive framework for early disease detection and welfare deterioration using logistic regression and time-series analysis; and (5) proposing evidence-based welfare and biosecurity interventions tailored to urban zoo koala populations. A mixed-methods approach integrates retrospective quantitative analyses with prospective longitudinal monitoring over 24 months. The population comprises all koalas housed at three metropolitan zoos with urban-adjacent habitats, totaling 72 individuals (38 females, 34 males; age range 1–22 years). The sample includes all koalas with complete veterinary records and a stratified subset (n=40) selected by age and enclosure type for enhanced welfare monitoring. Data collection instruments include (i) veterinary clinical records and laboratory test results (PCR assays for Chlamydia pecorum, serology for Koala Retrovirus, and nasopharyngeal/ conjunctival swabs); (ii) welfare assessment protocols integrating qualitative behavioral assessments (identified through an ethogram) and quantitative metrics such as fecal glucocorticoid metabolites (FGMs) measured monthly via enzyme immunoassay; (iii) environmental monitoring devices recording temperature, humidity, noise, and visitor density; (iv) enclosure- and diet-related records including enrichment schedules, substrate types, and foliage availability. Validity and reliability are ensured through cross-validation of clinical diagnoses with laboratory results, calibration of FGM assays against known stressors, inter-observer reliability checks for behavioral coding, and pilot testing of enrichment scoring rubrics. Statistical analyses will employ descriptive statistics, chi-square tests for prevalence comparisons, and generalized linear models to examine associations between disease status, welfare indicators, and environmental/management predictors. Time-series analyses will assess trends and lag effects between environmental variables and welfare/disease outcomes. Model specification will include interaction terms to explore moderation effects of enclosure type and enrichment on disease risk. The study will apply the theoretical lens of the biopsychosocial model of animal welfare and the One Health framework to interpret interdependencies between animal health, environmental context, and public health considerations. Expected findings include (a) identification of higher Chlamydia pecorum exposure and subclinical infections among younger males in high-visitor-density enclosures; (b) significant correlations between elevated FGMs and reduced body condition, increased abnormal behaviors, and positive disease status; (c) robust associations between climate stressors (extreme temperatures and high humidity) and spikes in respiratory pathogens, moderated by enrichment frequency and diet quality; and (d) predictive models achieving substantial accuracy (AUC > 0.80) for early detection of welfare decline and disease onset. The study is anticipated to contribute to knowledge by integrating disease surveillance with welfare assessment in urban zoo koalas, demonstrating how urban environmental pressures influence pathogen dynamics and welfare, and providing a transferable framework for zoo-based disease monitoring within the One Health paradigm. The main conclusion will emphasize the critical role of continuous welfare monitoring and proactive enrichment, biosecurity, and environmental management in mitigating disease risk. Recommendations include implementing standardized, rapid diagnostic workflows, routine enrichment-based behavioral interventions, targeted health screenings aligned with seasonal climate variation, and policy guidance for urban zoos to harmonize animal welfare with public health responsibilities.