Koalas’ survival is increasingly threatened by chlamydia – but there is hope

Chlamydia in koalas

It has long been known that koalas can become infected with chlamydia. The disease was already widespread in the South East Queensland region 26 years ago. Researchers discovered this when they analyzed reports from three animal hospitals. According to this report, about 30 percent of all koalas brought in between 1997 and 2013 were infected with chlamydia. However, how widespread the disease actually was among local koala populations in these years could not be deduced from these figures.

More accurate data on the spread of the disease is available from a koala population in Gunnedah, a small town in northeastern New South Wales. According to Mark Krockenberger, a professor of veterinary pathology at the University of Sydney, 10 percent of the population was infected with the bacteria in 2008. In 2015, the number rose to 60 percent and now 85 percent of all koalas in this population are infected.

The risk of infertility

Chlamydia infection in koalas has many consequences. It can cause eye diseases affecting one or both eyes and lead to blindness in chronically ill koalas. The bacteria often cause problems in the urinary tract and genitals as well. Koalas can become incontinent because of this, although the disease can easily be recognized by the so-called “wet soil”. This refers to the brown discolored posterior area caused by incontinence. In women, chlamydia can lead to ovarian cysts and eventually infertility.

The autopsy of a female koala with advanced chlamydia disease revealed just how cruel such a disease can be. The ovaries were completely surrounded by cysts, recalls Rebecca Johnson, who previously led Australia’s large “Koala Genome” project. The intestines were also full of hard chunks of food, which indicated that the animal could no longer digest the food. The animal’s condition broke her heart, Johnson told AP News:

A 2018 study concluded that a chlamydia infection often leads to death. Of the 291 koalas studied in Queensland over a four-year period, 18 percent died of chlamydia or related complications.

An even greater threat to koala populations, however, is female infertility: Populations like the one in Gunnedah, where 85 percent of all koalas are infected, are no longer viable. Professor Krockenberger explains to CNN:

Researchers suspect that koalas were first infected by contaminated cattle or sheep feces and that the disease spread to the koala population. Like humans, chlamydia spreads from koala to koala through sexual contact. In addition, the koala mother can pass the bacteria on to her babies.

It is threatened with extinction

This is a major problem as Australia’s koala populations are already threatened by other factors. They were once widespread in Australia but were widely hunted for their fur, especially after the arrival of the Europeans. Hunting koalas was so popular that they were completely wiped out in South Australia around 1924. In 1937, the government declared the koala a protected species nationwide.

However, the danger to the marsupial was not over: the shrinking habitat due to deforestation and forest fires became an increasing threat in the following period and still is. Attacks by wild dogs and vehicle collisions often result in the deaths of the animals. In some regions of Australia, the koala population has declined by 80 percent since the 1990s, according to an analysis by the WWF.

Researchers suspect that all of these threats promote the spread of chlamydia because the associated stress weakens the koala’s immune system.

By the way, sleeping koalas are so cute:

1/13

Sleeping koalas

source: shutterstock

New vaccination gives hope

Although the shrinking habitat can be counteracted with protection zones, the danger of chlamydia has not passed. Animal rights activists and veterinarians face a major challenge: Treating infected koalas is difficult because they spend most of their lives in eucalyptus trees and are therefore difficult to reach. In addition, antibiotic treatment has proven less than ideal in the past, as the drugs upset the sensitive stomachs of the animals too much. Although some animals were cured of chlamydia, they subsequently had problems digesting eucalyptus leaves – their main source of food.

That’s why the University of the Sunshine Coast has been researching another solution for more than 10 years: a special chlamydia vaccine for koalas. As early as 2021, the researchers ushered in the third phase of the study, in which up to 400 koalas brought to animal hospitals for other reasons were vaccinated.

Peter Timms, a professor of microbiology at the University of the Sunshine Coast and co-developer of the vaccine, told CNN in 2021 that he was optimistic about the newly developed solution:

In March this year, his team began vaccinating wild koalas in the state of New South Wales. The researchers aim to capture, vaccinate and monitor half of the koala population in the Northern Rivers Region. Specifically, there are 50 koalas. The aim of this experiment is to find out how many koalas in a wild population would need to be vaccinated to achieve a significant reduction in infection.

Vaccinating wild animals is an extremely time-consuming endeavor that has not yet been taken up by many researchers worldwide. But the project is important — and time is of the essence: according to a 2020 New South Wales government report, koalas could become extinct by 2025 due to a combination of threats, including disease, habitat loss and traffic accidents.