Chlamydia has spread to Sydney’s only disease-free koala population with two koalas testing positive after they were rescued late last year.
The koalas were tested after they were found in Appin in south-western Sydney in September with injuries suggesting they had both been hit by cars.
One koala was treated while the other had to be euthanised, the New South Wales environment department said.
The south-western Sydney koala population, which includes Appin and Campbelltown, is one of only a few koala populations in NSW free of chlamydia, which causes infertility and has severely affected populations elsewhere in the state.
Chlamydia positive and chlamydia negative populations of koalas meet on the Woronora Plateau at Picton Road, 10.5km south of Appin.
The government said it had moved quickly to introduce additional biosecurity measures and establish a working group that includes wildlife carers and researchers at the University of Sydney.
But it did not make the positive detections public at the time.
The department said surveys and testing of “wild koalas in the vicinity of where the chlamydia positive koalas were found” had been conducted and had found no further evidence of the disease. The department did not say how many koalas had been tested.
“We responded to this incursion quickly and will continue to improve our understanding of the most effective interventions,” said Alison Schumacher, the department’s director of threatened species and ecosystems.
“We are working closely with our partners to manage this disease and protect this much-loved species.”
Saul Deane, the urban sustainability campaigner at the Total Environment Centre, said the positive detections of chlamydia were “a really depressing development”.
“It would be devastating if it becomes endemic in the local population because it’s one of only a few in the state where chlamydia is not the main cause of mortality,” he said.
The department said it would continue monitoring for the disease and would expand testing in coming months by using drones east of Appin to locate koalas and collect their scats for testing.
It is also long-established practice that every koala that is rescued and taken in to care is tested for chlamydia.
Professor of veterinary science Mark Krockenberger is leading a University of Sydney research team that has been commissioned to develop a chlamydia management strategy for delivery to the NSW government by the end of the year.
Krockenberger has been involved in research for the past few years that has been trialling a vaccine to determine if it can be used to create a barrier between koalas with chlamydia in the southern highlands and the disease-free populations in Appin and Campbelltown.
He said while the positive detections in September were a “serious” development, “we’ve done a lot of tests which have not detected any more chlamydia”.
This article by Lisa Cox was first published by The Guardian on 20 March 2025. Lead Image: Chlamydia causes infertility and has severely affected koala populations.
Photograph: Matthew Starling/Getty Images.
What you can do
Wildlife continues to face threats, which include hunting, poaching, illegal trade in animal products, habitat loss as well as a rapidly changing climate.
Become a Wildlife Champion today by supporting our conservation partners with a monthly donation as little as $1.
