Deadly Chlamydia Threatens Koalas Down Under

koala, chlamydia
The koala (Phascolarctos cinereus) is often inaccurately referred to as a bear. Nearly 100 percent of some wild populations in Austrailia are being affected by chlamydia, a potentially lethal bacterial infection. Pacific Press/LightRocket/Getty Images

Kookaburras in the gum trees do it. Kangaroos in the outback do it. Koalas in the eucalyptus leaves do it. But when koalas do it, they fall ill with a debilitating and extremely painful sexually transmitted disease: chlamydia. And it's ravaging the population of Australia's iconic tree-hugging, leaf-munching, sleepyheaded marsupial.

Over the past 20 years, koala populations in certain areas of Australia have decreased by nearly 80 percent due to loss of habitat and being killed by cars, as well as dying from disease. A Feb. 21, 2017 article in Science Daily cites a two-decade study by the University of Queensland, Australia, that analyzes data on koala mortality and disease. The study confirms that chlamydia is a serious factor in the dramatic escalation of koala fatalities. And some surveys have demonstrated that the potentially lethal bacterial infection affects 100 percent of some wild populations.


While chlamydia has sickened koalas for decades, it wasn't clear until now what makes them so susceptible to the disease. According to a study in the March 2018 issue of the Journal of Virology, scientists have discovered that koalas infected with a virus they call koala retrovirus type B (in the same family as HIV, or human immunodeficiency virus) could be the offender. The presence of the retrovirus type B in conjunction with chlamydia makes them more vulnerable to the havoc of severe bladder problems, blindness, infertility and certain cancers. And young koalas aren't exempt. They can contract it from their momma's pap, a nutritious form of feces used to wean little joeys.

Chlamydia-infected koalas are treated with antibiotics, same as chlamydia-infected humans. But the koalas don't respond well to the drugs and after treatment they often lose weight and die. One study shows that the antibiotics interfere with their gut bacteria and disrupt the ability to digest their staple diet of eucalyptus leaves, rendering the drugs meant to save them as a source of their demise.

On Sunday, May 6, HBO's "Last Week Tonight" host, John Oliver, threw levity in the face of the koala's weighty plight when he announced the dedication of the John Oliver Koala Chlamydia Ward to treat ailing koalas at the Australia Zoo Wildlife Hospital. He wrapped the show with, "Now if you'll excuse me, I have a date with some very contagious koalas."

Pretty funny stuff, unless you're a sick or dying koala. But sometimes you just gotta laugh to keep from crying.