Credit: University of the Sunshine Coast
The first vaccine to prevent chlamydia infections in koalas has been approved by the Australian Pesticides and Veterinary Medicines Authority.
The high-quality, veterinary-approved product can now be used in wildlife hospitals, veterinary clinics and in the field to protect the nation’s most at-risk koalas, says Professor Peter Timms, who led the research at the University of the Sunshine Coast’s (UniSC) Centre for Bioinnovation.
“We knew a single-dose vaccine – with no need for a booster – was the answer to reducing the rapid, devastating spread of this disease, which accounts for as much as half of koala deaths across all wild populations in Australia,” says Timms.
“Some individual colonies are edging closer to local extinction every day, particularly in southeast Queensland and New South Wales, where infection rates within populations are often around 50% and, in some cases, can reach as high as 70%.”
In koalas, infection with Chlamydia pecorum can cause chronic and painful conditions – such as blindness, urinary tract infections and infertility – and may even result in death.
“In the wild, a koala might live for 10-15 years, but a severe infection could reduce this to 5-7 years or less,” the researchers wrote in the largest and longest-ever study of wild koalas, published last year in npj Vaccines.
Professor Peter Timms. Credit: University of the Sunshine Coast
Currently, koalas with chlamydia are treated with antibiotics – chloramphenicol or doxycycline. However, this can disrupt bacteria in the gastrointestinal tract, and therefore a koala’s ability to digest eucalyptus leaves, leading to starvation and sometimes death.
What’s more, prior infection and treatment with antibiotics does not prevent a koala from becoming infected again in the future.
After a decade of work and several trials, the safety and efficacy of the vaccine was confirmed last year in the npj Vaccines study.
“This study found that the vaccine reduced the likelihood of koalas developing symptoms of chlamydia during breeding age and decreased mortality from the disease in wild populations by at least 65%,” says the UniSC senior researcher who led the research, Dr Sam Phillips.
“The vaccine has been trialled on hundreds of wild koalas, others in captivity and wildlife hospitals, and over multiple generations.
“It’s based on Chlamydia pecorum’s major outer membrane protein (MOMP), and offers 3 levels of protection – reducing infection, preventing progression to clinical disease and, in some cases, reversing existing symptoms.”
Credit: University of the Sunshine Coast
The vaccine contains 6 main components. These include the vaccine’s ‘active ingredients’, which trigger an immune response, and the ‘adjuvant’ – a substance which increases the immune response to the active ingredients.
“Three are the proteins of chlamydia, designed to cover the different strains of chlamydia circulating in different parts of the country,” says Timms.
“There are also 3 parts to the adjuvant, which we are very pleased to have designed as a single-shot adjuvant. Many vaccines require a booster, but we’ve purposely developed a vaccine that only requires one shot, and for wild animals like koalas, that is what you really need.”
This minimises logistical issues for teams working to capture koalas in the field, and reduces stress to the koala caused by handling.
The researchers plan to secure funding and donations to deliver the vaccine to 1,000 of the most vulnerable koalas in 2026, enable ongoing monitoring and fieldwork and conduct ongoing research to ensure its long-term success.