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Immuno-histochemical demonstration of the role of Chlamydiaceae in renal, uterine and salpingeal disease of the koala, and demonstration of Chlamydiaceae in novel sites

Higgins, DP, Hemsley, S & Canfield, PJ 2005, Journal of Comparative Pathology, vol. 133, no. 1, pp. 164-174.

The purpose of this study was to examine the distribution of chlamydial organisms in the kidneys and female upper reproductive tract of the koala and consequently characterise their role in disease. It was found that Chlamydiaceae contribute significantly to renal, uterine and salpingeal disease. Additionally, the report details a case study of a concurrent systemic infection with Chlamydiaceae and Gram-positive cocci.

  Tissue samples were collected from diseased koalas including sections of the lung, kidney, ureter, bladder, urogenital sinus, vaginal complex, cervix, uterus, ovary and salpinx. Swabs taken from the urogenital sinus were tested for the presence of chlamydial DNA. Tissue samples from deceased koalas revealed the presence of Chlamydiaceae in epithelial cells and macrophages in association with pyogranulomatous pyelonephritis (inflammation of the kidney characterised by infiltration of polymorphonuclear cells), focal interstitial nephritis (inflammation of the spaces between the kidney tubules) and active inflammation and fibrosis of the upper female reproductive tract. In one of the cases of pyelonephritis observed, Gram-positive cocci were detected in association with Chlamydiaceae. In another case of pyelonephritis, filamentous bacteria carried in the blood seemed to be the cause of the disease. Chlamydial metritis (inflammation of the uterine wall associated) was found in three instances to co-occur with other bacterial infections. In these cases, the chlamydial infection may be the primary causative agent of the disease, or it may induce, exacerbate or otherwise modify the reaction to non-chlamydial bacteria at the site. Furthermore, chlamydial inclusions were detected within pulmonary macrophages and epithelial cells in association with pneumonitis, and in one koala were detected in splenic and hepatic macrophages. The authors suggest that macrophages may act as sites of latent, persistent chlamydial infection that may eventually spread systemically.

  The results of this study have several implications. Firstly, the findings confirm that anti-chlamydial drug therapy is appropriate in cases of renal, uterine or salpingeal disease given the potential for Chlamydiaceae to be implicated in these diseases. The revelations also shed light on the causative factors of such diseases. Finally, the authors indicate that similarities between models of chlamydial disease in koalas and humans may create opportunities for the application of tools for studying the pathogenesis and epidemiology of the disease in humans to koalas, or vice versa.


Summarised by Joanna Horsfall


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