The main image is of koalas ‘Leah’ and ‘Paula’. Image provided by Dr Rosie Booth, Australia Zoo Wildlife hospital (Beerwah, Queensland).

Chlamydiosis is the most prevalent infectious diseases in koalas. This disease is caused by bacteria of the Chlamydiae species. The disease infects the soft tissues such as the tissues (conjunctiva) around the eyes and it can affect the reproduction organs and the bladder and urinary tract, resulting in a very painful bladder infection, otherwise known as ‘wet bottom’.

Australia Zoo Wildlife hospital vets, led by Dr Rosie Booth has had very good success treating koalas chlamydiosis with a weekly dose of a doxycycline injection into the tissues just under the skin for 4 weeks. The koalas in the main picture had chlamydiosis of the eyes and have been treated with doxycycline injections and their eyes look so much better!

Australia Zoo Wildlife Hospital has been working with our laboratory to check that the dose being administered to infected koalas is likely to kill the chlamydia bacteria that live inside the koalas’ tissues. This study is happening very slowly due to the demands for wildlife veterinarians to assist in treating injured wildlife. However what has been achieved so far:

Australia Zoo Wildlife hospital has administered doxycycline at 5 mg/kg by a subcutaneous injection once per week for four weeks to two koalas with chlamydiosis.  They collected blood samples over 4 weeks and my laboratory has analysed the blood samples for the doxycycline concentrations as shown in the following graph:

Doxy plas conc Ant & Bob Hawke 0 -96 h.

The dotted line at 100 ug/mL indicates the theoretical doxycycline concentration in the blood that will inhibit chlamydial pathogens.

What can be taken form the doxycycline blood concentrations taken from these two koalas:

Based on a blood concentration to kill chlamydia pathogens may be 100 ug/mL (taken from Fukushi,H, Ochiai Y, Yamaguchi T and Hirai K (1998). In vitro susceptibility of Chlamydia pecorum to macrolides, tetacyclines, quibolones and beta-lactam. Microbiologu and Immunology, 42, 61 – 63)  then twice weekly injections may be more efficacious to inhibit the pathogen. But if once weekly administration results in the improvement of clinical signs as seen in Leah and Paula above, then the clinical response is the best indication of a successful drug dosage success.