Scientists are vaccinating koalas against chlamydia

Scientists in Australia are vaccinating wild koalas against chlamydia in an attempt to stop the sexually transmitted disease from wiping out the population.

A team of scientists aims to catch and vaccinate about 50 koalas in the Northern Rivers region of New South Wales as part of a government-approved field test to thwart the disease which causes blindness, infertility and death in the animals.

Chlamydia, along with habitat loss and car crashes, has put the marsupials at risk of extinction in less than 30 years, according to a 2020 assessment from the New South Wales government. The Australian government declared koalas an endangered species throughout the eastern regions of New South Wales, Queensland and the Australian Capital Territory.

“It’s killing koalas because they become so sick they can’t climb trees to get food, or escape predators, and females can become infertile,” University of the Sunshine Coast microbiologist Samuel Phillips told the Associated Press.

The vaccination effort began in March after scientists had first vaccinated a few hundred koalas that were being rehabilitated for unrelated issues at wildlife rescue centers.

“We want to evaluate what percentage of the koalas we need to vaccinate to meaningfully reduce infection and disease,” said Phillips, who helped develop the single-shot vaccine.

In order to give the wild marsupials the shot, the researchers search for them in trees and re-route them into cages when they climb down.

Veterinarians then check that the koala is healthy and administer anesthesia and the vaccine. They keep the koalas for 24 hours to ensure they have no unexpected side effects.

The vaccinated koalas are marked with pink dye on their backs and released back in the wild.

The effort to vaccinate half of the Northern Rivers region’s population is expected to take around three months.

Unlike in humans, chlamydia in koalas cannot be treated with antibiotics because the animals have microbes in their stomachs which neutralize toxins in eucalyptus leaves but also often neutralize the effects of antibiotics, said Mathew Crowther, a conservation biologist at the University of Sydney. As a result, researchers created a vaccine specifically for koalas to make them immune to the STD.

Scientists don’t know how chlamydia originated in koalas, but believe they may have been infected through exposure to the droppings of livestock who had the disease. The disease was then spread through intercourse or passed from a mother koala to her babies.

One koala who had advanced chlamydia and was euthanized has cysts surrounding her ovaries and was unable to digest her food, according to Smithsonian scientist Rebecca Johnson, who previously led the Koala Genome Consortium in Australia.

 “She was obviously infertile and in pain,” Johnson said, calling the disease’s effects heartbreaking.

The disease has spread rapidly through the koala population.

In 2008, just 10% of koalas tested in northern South Wales were positive for chlamydia. Now 80% have been infected, according to Crowther who has been monitoring the population for years.

“It’s been devastating — there’s very, very low fertility,” he said. “You hardly see any babies.”

With Post wires