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Koala translocations and Chlamydia: Managing risk in the effort to conserve native species

Waugh, C, Hanger, J, Timms, P & Polkinghorne, A 2016, Biological Conservation, vol. 197, no. 1, pp. 247-253.

Despite becoming more commonly accepted as a ‘last-resort’ strategy for protecting at-risk animals, koala translocation may have a negative net impact upon the conservation of the species because of the associated risk of spreading chlamydial disease. In the context of recent scientific developments regarding the biology and epidemiology of Chlamydia pecorum infections in koalas, the authors of this report discuss the risks associated with koala translocations and potential management strategies for those risks.

  Disease associated with C. pecorum infection is a major threat to koalas, the severity of which has sparked great research interest in the disease and tools for its prevention. These developments revealed some potential challenges to the success of a koala translocation programme. A translocation event must not introduce a pathogen into the recipient population, but the health of donor and recipient populations is made difficult to assess by the widespread yet asymptomatic nature of Chlamydia in koalas. Furthermore, the strain of C. pecorum that infects the translocated individual may be genetically distinct from that present in a recipient population. In addition to pathogen transfer between koalas, ‘spillover’ from koalas to livestock, or vice versa, is also possible. The consequences of this cross-host transmission can be devastating both ecologically and economically. Finally, translocation presents the risk of cross-host transmission of koala retrovirus (KoRV) as well as the introduction of KoRV to a previously unaffected population, yet these risks are poorly understood at present. To minimise risk, before a translocation occurs practitioners must: (a) screen both donor and recipient populations for Chlamydia; (b) put in place mitigation strategies to avoid transmission of unique Chlamydia genotypes into a recipient population, and (c) devise strategies to mitigate the risk of ‘spillover’ between species.

  Translocation of koalas has occurred for many decades and purposes, yet only recently has it emerged as a potential conservation strategy for declining northern koala populations. In south-east Queensland, this threatened species is increasingly displaced by urban sprawl, and thus the possibility of moving displaced individuals from one habitat to another is a seemingly viable mitigation option. In the past, translocations have failed because of, or been challenged by, overlooked factors including infectious disease dynamics. Thus, before such programmes become more commonplace, it will be essential to establish tools and protocols that ensure their success.

  In addition to the risks associated with pathogen transfer, there are a number of factors involved in koala translocation that must be resolved if any such programme is to be successful. These factors relate to genetics, habitat carrying capacity, regional population conservation, and the acceptability of translocation programmes to the broader community. In light of the risks discussed in this paper, a crucial next step in defining translocation protocols is establishing standardised veterinary procedures for assessing and managing infection transmission risk and post-release monitoring of translocated koalas and recipient populations.

 

Summarised by Joanna Horsfall

 

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