Koalas in Queensland show signs of immunity to deadly retrovirus

Koalas in a population north of the Brisbane River are showing a surprising genetic resistance to a virus that has weakened their species for generations.

Scientists have discovered that some of these koalas have developed a unique genomic immunity to the retrovirus that suppresses their immune system and makes them more vulnerable to infections like chlamydia and even cancer.

Researchers from The University of Queensland and UMass Chan Medical School made the discovery while studying koala populations in different regions.

The findings, published in the journal Cell, could be a key step in efforts to protect one of Australia’s most iconic animals.

Koalas’ hidden immunity

Koalas infected with the retrovirus are at a higher risk of chlamydia, which has devastated populations in Queensland and New South Wales.

The virus has also been linked to lymphomas that have caused significant mortality in captive koalas.

However, scientists found that about 30% of koalas in the Sunshine Coast hinterland have a genetic adaptation that suppresses the virus.

“What we found is that there is a single genetic switch that has been activated in about 30% of the koala population in the Sunshine Coast hinterland, suppressing the retrovirus,” said Professor Keith Chappell, a virologist at the Australian Institute of Bioengineering and Nanotechnology.

“This is in contrast to what we found in the population on the Gold Coast, where this adaptation is almost completely absent.”

A natural defense spreading over time

The study, led by research fellow Dr. Michaela Blyton, suggests that this adaptive genomic immunity functions similarly to how an immune system strengthens after exposure to pathogens.

“Because this ‘genomic immunity’ can be inherited, the discovery suggests koalas with the trait could be used in breeding programs to reduce the susceptibility of other populations to the retrovirus, like on the Gold Coast,” said Dr. Blyton.

The researchers also found evidence that this adaptation is spreading through the northern koala population, though it will take generations to fully establish itself across the region.

A rare opportunity to study evolution

Professor Chappell explained that retroviruses can alter the genetic code of a species over time. In humans, about 8% of DNA comes from retroviral infections that occurred over millions of years.

In contrast, the koala retrovirus only entered the marsupial’s genome a few thousand years ago, which is considered very recent in evolutionary terms.

“Out of all the species on the planet, this is the only one where we can see a genetic response to a retrovirus in real time, rather than looking at responses to things that got into the genome millions of years ago,” said Professor Chappell.

“This allows the researchers to study exactly how these iconic critters are responding – it’s actually a pretty amazing situation.”

Genetic adaptations of koalas

At the University of Massachusetts, Professor William Theurkauf had spent decades studying fruit flies and their genetic responses to genome invaders.

When he learned about the koala research, Professor Theurkauf saw clear parallels with his work and an opportunity for collaboration.

Despite the vast differences between fruit flies and marsupials, both studies shed light on how species develop genetic defenses against viral threats.

This trans-Pacific partnership has helped scientists gain deeper insight into how koalas are adapting at the genetic level.

Building stronger koala populations

The researchers caution that while the retrovirus is not the most immediate threat to koalas, understanding this genetic adaptation could improve conservation efforts. Habitat destruction and climate change remain the biggest dangers to koala populations.

By identifying populations with a natural resistance to the retrovirus, conservationists can develop targeted strategies to enhance the species’ resilience against disease.

Koalas with this trait may be better suited for repopulation efforts in areas where disease has significantly reduced their numbers.

This discovery could lead to breeding programs that prioritize koalas with this genetic resistance, helping to build stronger populations that are less vulnerable to disease.

Scientists are now eager to explore whether similar adaptations exist in other koala populations across Australia, potentially opening new doors for conservation strategies in the years to come.

The full study was published in the journal Cell.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–