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Health and Disease




Disease and Health.

The overall health status of koalas in the Macedon Ranges Shire is unknown. We can assume that the populations are reasonably healthy due to the lack of significant disease present in koalas that come in to care to rehabilitators.

There have been cases of koala blindness that is yet to be explained and also testicular abnormalities, thought to be due to in-breeding of the koalas translocated to the area in the past.





Chlamydia is a bacterial pathogen that causes chronic infections in koalas.

The infections occur in the urogenital tract (C. pecorum) and the respiratory tract (C. pecorum and C. pneumoniae) and can cause infertility (in female koalas), blindness and ultimately death. The visible symptoms are conjunctivitis ('pink eye') and urinary tract infections causing incontinence, leading to a condition known as 'dirty tail' or 'wet bottom'.

Scientists now believe that the chlamydia organism has been occurring amongst koala populations for many years, and has acted as a natural  population control in times of stress. The organism is harmless in populations with unlimited resources, but manifests in times of  stress, such as happens when habitat is reduced. The weaker animals succumb to the disease, become sick, infertile or die, leaving the  genetically stronger animals to continue breeding. In disease-free populations which have been moved to areas where they were not native or where there is not enough habitat to support them (such as on some islands off Victoria and Kangaroo Island in South Australia), problems with overpopulation have arisen because of this unnatural situation. However, this is not the case in most mainland populations, and indeed many of the mainland colonies are in decline. Koalas also suffer from a range of cancers like leukemia and skin cancers.


  It is believe that most of the koalas in the Macedon Ranges might be Chlamydia positive, but this cannot be confirmed. 

We have had no reported sightings of koalas showing external signs of chlamydia to date.


                                    alt                  alt

                             Conjuctivitis                                      Wet bottom or Dirty tail



Koala Retrovirus

Koala Retrovirus is an endogenous (inherited) virus of koalas (Phascolarctos cinereus). It has not been detected in other species. Testing of a variety of native Australian vertebrate species for KoRV viruses is currently. There is no evidence for human infections with KoRV to date.