UPDATED PETITION AS OF NOVEMBER 8 2013
Disease is part of the natural history of the koala. There are 4 common koala diseases caused by the chlamydia organism: conjunctivitis which can cause blindness, pneumonia, urinary tract infections and reproductive tract infections, which can cause female infertility. The symptoms of chlamydia manifest as sore eyes, chest infections, and "wet bottom" or "dirty tail". Different strains of chlamydia bacteria are thought to cause these diseases. In 1995, scientists isolated two strains called chlamydia pecorum and chlamydia pneumoniae.
Scientists now believe that the chlamydia organism has been occuring 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.