Koala chlamydia crisis leads scientists to consider a cull of the cuddly animals

It’s been a grim month for Australia’s koala population, with scientists Down Under stating that around half of the country’s entire population is now suffering from a nasty and highly virulent strain of chlamydia, and one expert even suggesting that the only way to save the iconic animal might be to start killing them.

The type of chlamydia that has hit the animals so hard is slightly different to the disease that afflicts humans, although it is believed that people can catch the koala strain if they come into contact with the marsupials’ urine. Other species that suffer from the disease include crocodiles, but it’s koalas that appear to be most at risk of the infection in its most vicious form.

So, why do koalas suffer so badly from this disease? The answer, according to evolutionary biologist Suzanne Sadedin involves some seriously adult themes, including more sex and violence than you might think possible for such a lazy-looking tree-hugging bundle of fur. Despite spending up to 20 hours of every day in a dope-induced doze because of their heady eucalyptus diet, wild koalas really make the most of their four-hour active period, with males getting into regular punch-ups and females leading highly promiscuous sex lives. The result is that body fluids including blood, semen, urine, faeces and other excretions are liberally shared around, and all of these can carry the chlamydia pathogen.

And once transmitted, the bacterial disease can prove fatal to the marsupials. It’s excruciatingly painful for the animals, and even if it doesn’t kill them, it can leave victims blind and infertile, with a secondary infection known as ‘dirty tail’.

‘Dirty tail is actually really awful,’ David Wilson, professor of infectious diseases at the Burnet Institute in Melbourne, told the BBC. ‘The urinary tract gets inflamed and expands substantially; it’s incredibly painful. They get discharge and many koalas die.’

Koalas aren't as sweet and innocent as you might think
Koalas aren’t as sweet and innocent as you might think

Worryingly, despite being one of the most iconic faces of Australia’s unique collection of indigenous fauna, the leaf-munching marsupials are rapidly veering into endangered territory. Already adversely affected by severe habitat loss, koala populations have plummeted by 40 per cent in Queensland and around a third in New South Wales over the last two decades, and both regions added the animal to their list of threatened species in 2012.

Regardless of this, just last week a court ruled against conservation groups who are trying to stop a Chinese company from building a huge open-pit coal mine in New South Wales, 250 miles northwest of Sydney, in a region known as the koala capital of Australia because of its large, healthy population of the animals. The proposed development would definitely displace at least 260 koalas, and protesters fear the mine could contaminate an extensive aquifer that supports vast amounts of wildlife around the Liverpool Plains.

Koalas are also at risk from bushfires and attacks by introduced animals such as cats and dogs, but by far the biggest problem they face is bacterial infection, with many animals also suffering from a retrovirus a little bit like HIV, which makes the chlamydia all the more devastating. If caught early, scientists can potentially treat the infections with antibiotics, but koalas’ stomachs are full of bacteria that’s essential for digesting eucalyptus leaves, which would be killed by the systematic administration of antibiotics.

Koalas have bounced back from the brink before. They were almost hunted to extinction in the early 20th century, when the fur trade was responsible for around eight million deaths. Wilson says that, with up to 80 per cent of the animals in some closed koala populations around Australia infected with chlamydia, the problem has reached such a serious point that a large scale cull might be the only way to save the species.

Unsurprisingly, this is a contentious proposal, but Wilson believes it could pave the way for the wild koala population to recover within five to 10 years. A similar strategy was rolled out with an experimental cull of Tasmanian devils 10 years ago, in response to an epidemic of a deadly facial cancer spread between the animals by aggressive biting. Ultimately that cull didn’t work, but Wilson believes it was badly conducted.

A less controversial solution is being worked on by Professor Peter Timms at the University of the Sunshine Coast in Queensland, who is searching the koala genome for clues to how an effective vaccine might be developed. His team have sequenced one gene (IFN-g), which has been described as the ‘holy grail’ for understanding how the koala immune system works, and there are high hopes that this will prove to be an important weapon in the fight against the disease.

They are currently conducting trials of a prototype vaccine on 15 koalas at Steve Irwin’s Australia Zoo in Beerwah, Queensland, and early results have been positive. If successful, the lessons learned can also potentially be applied to the growing problem of chlamydia infection in young humans.