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Infection & disease

Pneumonia due to Chlamydia pecorum in a koala (Phascolarctos cinereus)

Mackie, JT, Gillett, AK, Palmieri, C, Feng, T & Higgins, DP 2016, Journal of Comparative Pathology, vol. 155, no. 1, pp. 356-360.

This report documents a case of Chlamydia pecorum infection of the bronchiolar epithelium of the koala, causing pneumonia in a juvenile male.

  Chlamydial infection and disease are widespread in most free-ranging koala populations. Causative relationships have been established between chlamydial organisms and keratoconjunctivitis, urinary tract inflammation, reproductive tract inflammation and colitis. Although Chlamydia is also associated with rhinitis/pneumonia complex, no causative effect of the pathogen has been confirmed. The authors of this study describe initial evidence of such a causative relationship. A juvenile male koala presented to a Queensland wildlife hospital exhibited symptoms of respiratory compromise. Under anaesthesia, exudate originating from the epiglottis/larynx was sampled and found to be positive for C. pecorum. Despite receiving immediate treatment, the koala died days later. During subsequent necropsy, a number of lung tissue abnormalities were detected including pyogranulomatous bronchopneumonia, proliferation of bronchiolar and alveolar epithelium, and interstitial fibrosis. Using transmission electron microscopy (TEM) and immunohistochemistry, cytoplasmic inclusions detected in many hyperplastic bronchiolar epithelial cells were found to contain chlamydial organisms of different developmental stages. Ranging in size, the organisms included both chlamydial elementary bodies, which are the infectious particles of the pathogen, and reticulate bodies, which are larger and metabolically active. These organisms were confirmed as C. pecorum via real-time polymerase chain reaction (PCR).

  Although an association was formerly observed, this report provides evidence that C. pecorum can infect the bronchiolar epithelium in the koala and lead to symptoms of pneumonia. This discovery has implications for the detection and treatment of infection with C. pecorum in koalas.


Summarised by Joanna Horsfall


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