Wild koalas in Australia are now being vaccinated against chlamydia, which has spread rapidly through the species’ population.
Koalas infected with chlamydia can experience blindness, bladder infections, infertility, and death. The animals become too sick to gather food or escape predators – making the species more vulnerable and contributing to the overall population decline.
Initially, scientists involved with the effort wanted to vaccinate 50 koalas in the Northern Rivers region of the state of New South Wales. This is equivalent to half of the area’s koala population.
The vaccine was developed by researchers at the University of the Sunshine Coast specifically for koalas. It is a single shot and was tested on koalas who were receiving treatment for other medical 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 microbiologist Samuel Phillips to AP News.
The outlet noted that researchers had to weigh the “risk of disturbing the animals against the danger of allowing the disease to spread” when deciding to vaccinate wild koala populations.
“The trial was approved by multiple government bodies, including Australia’s agriculture department and New South Wales’ planning and environment department,” reports AP News.
The Australian Koala Foundation estimated in September of 2021 that the nation’s koala population had declined by 30% since 2018. The marsupial was classified as extinct in 47 electorates while other regions had populations of just 5-10 koalas. Chlamydia is considered to be one of the leading causes of death among koalas.
In October 2021, USC and the Australia Zoo’s Wildlife Hospital had begun the third phase of its chlamydia vaccine trial. The trial involved 400 koalas, who were vaccinated and microchipped before being returned to the wild.
“While this vaccination will directly benefit each of the animals, the trial will also have a focus on the protection provided by vaccination,” Peter Timms, a microbiologist involved in the trial, told USA Today at the time.
“Although many koalas with chlamydia can be treated using traditional antibiotics, some animals cannot be saved due to the severity of their infection,” Dr. Amber Gillett, the Coordinator of Research and a wildlife veterinarian at the Australia Zoo Wildlife Hospital, said in a statement.”Having a vaccine that can help prevent both infection and the severity of the disease is a critical element in the species’ conservation management.”
Antibiotics used to treat the sexually-transmitted disease can disrupt the koala’s gut microbiome so severely they are unable to eat the eucalyptus leaves at the center of their diet.
The original cause of the chlamydia outbreak in Australia’s koalas is unknown. Some theories suggest the marsupials were exposed to the virus from exposure to feces from infected sheep and cattle. Scientists have theorized that the spread of a virus similar to HIV caused the rapid spread of chlamydia. Koalas that have the virus, called koala retrovirus type B, are more likely to contract chlamydia.