Chlamydia in wild Australian rodents: a cross-sectional study to inform disease risks for a conservation translocation

Context Chlamydia species impose major global burdens on both human and animal health. However, chlamydial infections of wild rodents have been understudied, posing limitations on assessments of disease risks for rodent conservation translocations. This is particularly true when there is evidence of infection in proposed source populations, as occurred for the Shark Bay mouse (Pseudomys gouldii) translocations to Dirk Hartog Island.Aims The aim of this study was to reduce uncertainty surrounding the risks posed by Chlamydia for these translocations by: (1) determining the presence, prevalence and diversity of Chlamydia in rodent populations in the Shark Bay region of Western Australia; (2) identifying associations with health parameters; and (3) assessing for evidence of cross-species transmission.Methods Swab, faecal and tissue samples from 110 wild-caught individuals (comprising five rodent and two marsupial species) were collected across four islands in Western Australia. These samples were analysed by a Chlamydiaceae 23s rRNA qPCR in a 14-month cross-sectional study conducted between 2020 and 2021.Key results In total, 20% of all individuals (22/110; 95%CI 13.6–28.4) from five species, including 19% (19/100; 95% CI 12.5–27.8) of rodents, were positive by the Chlamydiaceae qPCR, although in low loads. Further attempts at species identification of the Chlamydiaceae were unsuccessful. Our results found no detectable adverse health associations, or significant associated pathological findings, with low molecular loads supporting an asymptomatic infection state. Additionally, there were no disease associations in Shark Bay bandicoots (Perameles bougainville) despite the presence of an ocular disease syndrome previously linked to chlamydial infection in this species.Conclusions and implications Our findings suggest that sub-clinical chlamydial infections in wild Australian rodents may be widespread, but for the Dirk Hartog Island translocations, the risks of Chlamydia associated with movement of Shark Bay mice are likely low. The results highlight how current knowledge gaps pertaining to wildlife health can be addressed through collaborative approaches to translocation planning and implementation.