The ecology of chlamydiosis in the koala, Phascolarctos cinereus: Interactions between the host, pathogen and environment

Abstract

Effective management of threatened wildlife species in Australia remains a challenge given the multiple threatening processes species face, such as climate change, habitat loss and alteration, anthropogenic pressures, and disease. Across parts of its range, the koala, Phascolarctos cinereus, is listed as endangered to extinction and faces diverse threats to its survival, one of which is infection with the bacterium, Chlamydia pecorum. As chlamydiosis is an endemic disease impacting the fecundity and mortality of koala populations, it is intrinsic to the species ecology and population viability; particularly in the context of continued compounding challenges such as climate change, habitat degradation, loss and infection with other pathogens. The main aim of this thesis was to direct koala conservation management and research strategies by evaluating host, pathogen and environment features that interact together in complex relationships to drive disease and health. This was explored across two koala populations in New South Wales: The Liverpool Plains and Southern Highlands to South-west Sydney (SHSWS). Chapter 2, indicated that putative genetic virulence markers for C. pecorum in cattle were not suitable as indicators of virulence in koalas. However, they were consistent with short-term host pathogen evolutionary existence between koalas and C. pecorum and therefore appear likely useful to investigate the evolutionary trajectory of chlamydial strains in koalas. In Chapter 3, a novel typing tool was developed that revealed the emergence, diversity and movement of chlamydial strains across various habitat structures in a local management scale. Results of the study are informing plans to prevent incursions of C. pecorum into naïve populations. Chapter 4, used a multi-variate immunological approach to examine variation in koala immune profiles under varying geographical, climatic and co-infection contexts to evaluate their potential to impact disease susceptibility.