Abstract
Koalas (Phascolarctos cinereus) have suffered severe declines in the northern extent of their range due to a variety of threats, including habitat destruction, trauma from cars and dogs, climate change and importantly, disease. The most significant pathogen in koalas is Chlamydia pecorum, which causes inflammation and fibrosis at mucosal sites, resulting in blindness, infertility and death in severe cases. Chlamydia treatment can be problematic in koalas as the response to treatment is often poor in chronic cases and antimicrobial choice is limited. Thus, chlamydial disease is a severely threatening process for koala conservation. We investigated the short and long-term clinical outcomes for 167 koalas with Chlamydia that underwent capture, telemetric monitoring and intensive veterinary management as part of a large-scale population management program in South East Queensland. Chlamydia treatments included the standard regimen of daily subcutaneous chloramphenicol injections (60mg/kg) for 14 to 28-days, and a variety of non-standard regimens such as topical antimicrobials only (for ocular disease), surgical treatment only (for bilateral reproductive tract disease), and other antimicrobials/treatment lengths. To assess these regimens we analysed clinical records, field monitoring data and swab samples collected from the urogenital tract and ocular conjunctiva. Overall, in contrast to other studies, treatment was generally successful with 86.3% of treated koalas released back into the wild. The success of treatment rose to 94.8% however, when the standard treatment regimen was employed. Further, 100% of koalas that were also treated with surgical ovariohysterectomy (n = 12) remained healthy for a median of 466 days of post-treatment monitoring, demonstrating the benefits of surgical treatment. Previous studies reported 45-day chloramphenicol regimens, but the shorter standard regimen still achieved microbiological cure and reduces the risk of negative sequelae associated with treatment and/or captivity and treatment costs. Despite these positive clinical outcomes, alternatives to chloramphenicol are warranted due to its decreasing availability.
Highlights
Chlamydial infections caused by Chlamydia pecorum, and less commonly C. pneumoniae, are endemic in almost all free-living koala populations, with variable impacts on koala health [1,2,3,4]
In South East Qld (SE Qld) for example, the prevalence of infection and disease varies between sub-populations but can be as high as 85% and 52.5% respectively, with some studies reporting infertility in up to 57% of the females examined [1, 7, 8]
The Moreton Bay Rail (MBR) koala management program provided valuable data on the short and long-term clinical outcomes for a large number of free-living koalas treated for Chlamydia infection and disease
Summary
Chlamydial infections caused by Chlamydia pecorum, and less commonly C. pneumoniae, are endemic in almost all free-living koala populations, with variable impacts on koala health [1,2,3,4]. In South East Qld (SE Qld) for example, the prevalence of infection and disease varies between sub-populations but can be as high as 85% and 52.5% respectively, with some studies reporting infertility in up to 57% of the females examined [1, 7, 8]. Because of these impacts on morbidity, mortality and fecundity, chlamydial disease can substantially contribute to population declines and localised extinctions and is a severely threatening process for the conservation of the koala [9, 10]. Most free-living koalas presented to care facilities for chlamydial illness are suffering from chronic disease, complicating treatment
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