A series of recent studies by researchers at the University of the Sunshine Coast (USC) in collaboration with a range of partners across the country have revealed that (i) koalas are not the only marsupial hosts of chlamydial infections and that (ii) Chlamydia pecorum, the major pathogen of the koala, is not the only chlamydial species that can be found. 

In a report recently published in the journal, Scientific Reports (https://www.nature.com/articles/s41598-017-13164-y), the researchers found that C.  pecorum, could also be detected in common brushtail possums, squirrel gliders and spotted tail quolls in Queensland, New South Wales and, interestingly, Tasmania. No evidence of the characteristic signs of chlamydial disease could be found in these animals, however. How common these infections are and what impact they have for animal health is currently unknown but it does raise interesting new questions about the origin and relationships of these C. pecorum strains to those causing serious disease in koalas. 

 While the detection of C. pecorum in several new marsupial hosts was interesting, perhaps the most surprising discovery was the detection of DNA sequences related to several recently described new chlamydia found in a survey of Australian ticks (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5267465/). Over the last 20 years or so, the access to DNA sequencing technology has revealed an untapped level of diversity of bacteria related to the ‘traditional’ chlamydial pathogens of koalas, humans and domesticated animals. Indeed, many of these new bacteria can be found in surprising locations, including amoeba and arthropods such as ticks, cockroaches and flies. The current study found that the most common chlamydial infections detected in non-koala marsupials were of tick origin, suggesting that, like several other bacterial pathogens, these novel chlamydiae may be transmitted by tick bite. Studies are now underway to investigate the disease-causing potential of these novel chlamydial infections of Australian marsupials. 

The work was funded by Australian Research Council Discovery (DP130102066) and Linkage Project (LP150100722) grants and a Holsworth Wildlife Endowment Grant and forms the major component of the PhD studies of USC student, Delaney Burnard. Please contact Assoc Prof Adam Polkinghorne, University of the Sunshine Coast (apolking@usc.edu.au) for further information.