A Possible Link between the Environment and Nasal Colonisation in Koalas () in the Liverpool Plains, New South Wales.

Cryptococcosis caused by yeasts of the species complex is an increasingly important mycological disease in humans and other mammals. In Australia, cases of -related cryptococcosis are more prevalent in the koala () compared to humans and other animals, likely due to the close association that both and koalas have with species. This provides a cogent opportunity to investigate the epidemiology of spontaneous infections in a free-living mammalian host, thereby offering insights into similar infections in humans. This study aimed to establish a link between nasal colonisation by in free-ranging koalas and the tree hollows of species, the key environmental source of the pathogen. We (i) detected and genotyped from nine out of 169 free-ranging koalas and representative tree hollows within their home range in the Liverpool Plains, New South Wales, and (ii) examined potential environmental predictors of nasal colonisation in koalas and the presence of in tree hollows. Phylogenetic analyses based on multi-locus sequence typing (MLST) revealed that the koalas were most likely colonised by the most abundant genotypes found in the species, or closely related genotypes. Importantly, the likelihood of the presence of in tree hollows was correlated with increasing hollow size.