Koala chlamydia vaccine trialled by Australian researchers in bid to improve species’ survival

A chlamydia vaccine to treat koalas is being rolled out by Australian researchers in a trial they say could play a significant role in the long-term survival of the species.

From Friday, the chlamydia vaccine will be trialled in around 400 koalas at the Australia Zoo Wildlife Hospital in Queensland.

The vaccine is a single-dose jab that inoculates the marsupials against Chlamydia pecorum, a sexually transmitted bacterium that can result in infertility and blindness.

A wider rollout within the next three months is planned for the Moggill Koala Rehabilitation Centre and RSPCA Wildlife Hospital in Queensland, as well as several wild populations.

The researchers hope the vaccine will help to improve the survival and reproduction of the animals, especially in parts of south-east Queensland and New South Wales where chlamydia affects more than half of koala populations.

Threatened species experts warned earlier this year that koalas could soon be listed as endangered in Queensland, NSW and the Australian Capital Territory, due to habitat destruction devastating already struggling populations.

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Peter Timms, a professor of microbiology at the University of the Sunshine Coast, said the vaccine had previously been tested in eight smaller trials of around 250 koalas in total. “We know that the vaccine is safe. It causes no problems at all.”

Timms and his colleagues developed the protein-based vaccine over a decade. “We know that it can reduce infection levels,” he said, adding that the vaccine could also help to reduce the likelihood of chlamydia transmission.

“We’re pretty sure it’s predominantly sexually transmitted, but the mothers transmit it to their babies very effectively [too],” Timms said.

Koala chlamydia can result in conjunctivitis as well as painful fluid-filled reproductive cysts in females. “Animals can literally cry when urinating, it hurts them that much,” Timms said.

Chlamydia infection in humans is caused by a similar but distinct bacterium, Chlamydia trachomatis. While antibiotics can easily treat chlamydia is people, they are not ideal for the marsupials.

“You can’t really easily give antibiotics to koalas,” Timms said. “People do, but it upsets their gut bacteria, and they need their gut bacteria to digest eucalyptus leaves.

“Unfortunately 10 or even 20% of animals that go through the [Australia Zoo] wildlife hospital come back to the hospital. In a lot of cases, if you just treat them with antibiotics, they often come back with chlamydial disease again.”

All koalas in the Australia Zoo vaccine trial will be microchipped. The researchers plan to monitor koalas that return to the wildlife hospital for any reason over the following year, to study the differences between vaccinated and unvaccinated animals.

In parallel with the trials, the team is registering the koala vaccine with the Australian Pesticides and Veterinary Medicines Authority, which Timms described as “a “complicated, time-consuming, expensive project”.