Scientists are vaccinating wild koalas against chlamydia  | CBC Radio

Scientists are trying to save koalas from the disease that’s making their lives miserable and threatening the very survival of their species.

Researchers in Australia have developed a chlamydia vaccine specifically geared to the beloved marsupials, and they’re hoping it will help stop the sexually transmitted disease’s rampant spread.

In an ambitious new field trial, which began in March, they’re administering the vaccine to wild koalas in the state of New South Wales.

“Koalas are an iconic Australian species,” Samuel Phillips, a molecular biologist at the University of the Sunshine Coast who helped to develop the vaccine, told As It Happens host Nil Köksal.

“They do a lot for not only Australian tourism, but also for maintenance of the bush. They help clear leaves to stop a lot of wildfires spreading. They’re really important in the ecosystem of the Australian forests.” 

A species under threat

Koalas may appear, at first glance, to live lives of leisure. They sleep upwards of 20 hours a day, and spend many of their waking hours sitting in the treetops munching eucalyptus leaves.

But in reality, it’s not easy being a koala. Since 2022, they have been listed as endangered in eastern Australia. And an Australian government inquiry last year found that without urgent action to protect them, they could become extinct in New South Wales by 2050.

They face habitat loss from development and wildfires. They’re often hit by cars or attacked by dogs.

But one of their greatest threats is chlamydia, which can lead to blindness, widespread infertility, and fatal kidney failure.

In New South Wales alone, about 80 per cent of koalas are infected with the disease, according to Mathew Crowther, a conservation biologist at the University of Sydney who monitors the condition in koala populations. 

The origins of chlamydia in koalas aren’t confirmed, but many scientists suspect they initially caught it from exposure to the feces of infected sheep and cattle. Now it spreads sexually, or passes from mother to offspring.

But their unique biology makes them resistant to treatment.

“Koalas are exceptionally good at detoxifying agents, including antibiotics. So we have to give up to four times the dose of what we would for a normal animal, and prolonged doses,” Phillips said. 

“This ends up wiping out the koalas’ microbiome in their gastrointestinal tract, which is really important for koalas. They use the bacteria in their gut to detoxify eucalyptus leaves and also help with digestion. Without this bacteria, they end up starving to death.”

Catch, jab and release

So instead of just trying to cure chlamydia in sick koalas, scientists are now trying to prevent it in healthy ones. And they’ve already had some luck.

Vets at wildlife rescue centres in Queensland have already successfully tested the single-shot vaccine on a few hundred koalas who were brought in by other afflictions, Phillips said. 

But that approach has limits. Because the critters were often treated for multiple conditions, Phillips says it’s hard to properly monitor the vaccine’s effectiveness.

“Just vaccinating koalas [brought into] wildlife hospitals only results in about two per cent of the koalas being vaccinated,” he said. “And we estimate that we need to get at least 20 to 40 per cent of the population of koalas to be effective at lowering disease.”

So this time, they’re aiming to dose half the koalas in Northern Rivers region of New South Wales. That’s about 50 animals. 

Researchers use binoculars to spot koalas in eucalyptus trees, then construct circular enclosures around the tree bases with doors leading into cages. After a few hours or days, the koalas will eventually climb down from one tree to seek tasty leaves on another, and wander into the harmless traps.

After a check-up to make sure the animals are in good condition, researchers administer anesthesia, vaccinate them, then keep them under observation for 24 hours after they wake up, to confirm there are no unexpected side effects.

Each vaccinated koala is marked with pink dye to ensure they’re not trapped more than once, as well as as microchips and ear tags, to track their progress long term.

“We’ve done a little bit of modelling to show that hopefully, if we vaccinate 50 per cent of the population, we can achieve a 70 per cent reduction in the chlamydia infection rate within these koalas,” Phillips said. 

WATCH | Koalas downgraded from vulnerable to endangered:

Koalas declared endangered in eastern Australia

Australia’s much-loved koala has been moved from a vulnerable species to an endangered species as disease and loss of habitat threaten their survival.

If it works, the vaccine could not only help boost the koala population un Australia, but also dramatically reduce their suffering.

Chlamydia can infect koalas’ eyes, rendering them blind and unable to climb trees to find food or evade predators. It can also infect their urogenital tracts, causing bacterial infections, bladder inflammation or kidney failure.

Female koalas often develop cysts on their ovaries and become infertile.

Rebecca Johnson, chief scientist at the Smithsonian National Museum of Natural History in Washington, D.C., previously led the Koala Genome Consortium in Australia. She told The Associated Press that seeing the effects of the disease up close was heartbreaking.

A necropsy of one koala with advanced chlamydia that was euthanized revealed “ovaries completely encased in cysts” and “intestines full of hard lumps of food, evidence that she couldn’t properly digest food,” she said. 

“She was obviously infertile and in pain.”