Australian scientists start vaccinating wild koalas against chlamydia in a field trial

Australian scientists have begun vaccinating wild koalas against chlamydia in a field trial in New South Wales. The Associated Press reported that the vaccination aims to test a method for protecting koalas against chlamydia, a disease that causes blindness, infertility, and death.

The scientists aim to catch, vaccinate and monitor around half of the koalas in the Northern Rivers region of New South Wales. The single-shot vaccine’s safety and effectiveness were previously tested by vaccinating a few hundred koalas brought to wildlife rescue centres for other afflictions.

Now, scientists want to understand the impact of vaccinating a population of wild koalas.

Samuel Phillips, a microbiologist at the University of the Sunshine Coast, who helped develop the vaccine, said that the disease is killing koalas because they become “so sick they can’t climb trees to get food, or escape predators, and females can become infertile.”

The first koalas were caught and inoculated in March, and the vaccination effort is expected to last about three months. Scientists aim to evaluate what percentage of the koalas need to be vaccinated to meaningfully reduce infection and disease.

Scientists believe that chlamydia in koalas initially came from exposure to the feces of infected sheep and cattle. The disease then spread sexually or passed from mother to offspring. To vaccinate the koalas, scientists use binoculars to spot them in eucalyptus trees and construct circular enclosures around the tree bases with doors leading into cages.

After a few hours or days, the marsupials climb down from the trees and wander into these harmless traps. After a check-up to ensure that the animals are in good condition, researchers administer anesthesia and vaccine shots, then keep them under observation for 24 hours after they wake up to confirm there are no unexpected side effects.

Before the koalas are released, researchers mark them with a dab of pink dye on their backs to ensure the same animals are not caught twice.

The wild koala population in Australia has declined steeply in the last two decades. The government declared koalas “endangered” in the eastern regions of New South Wales, Queensland, and the Australian Capital Territory in February last year.

Scientists have estimated that half of the wild koalas in Queensland are already infected with chlamydia. In deciding to vaccinate marsupials, scientists are balancing the risk of disturbing the animals against the danger of allowing the disease to spread.