Australian scientists have found a clear link between stress levels and a higher risk of disease in koalas living in South East Queensland and along the New South Wales north coast.
Koalas carrying high levels of koala retrovirus (KoRV) become more vulnerable to deadly chlamydia infections, especially when habitat loss adds to their stress. A retrovirus is a type of virus that can get inside the cells of an animal and change its genetic material leaving it unwell or with a weakened immune system.
Scientists can use this new data to protect these at-risk populations, focusing on conserving habitats, selective breeding and exploring antiviral treatments.
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Dr Michaela Blyton from The University of Queensland led a study that monitored and measured the amount of koala retrovirus (KoRV) in both wild and captive koalas.
"We wanted to see what happened to their KoRV loads over time and how it related to chlamydial infection and levels of the stress hormones cortisol and corticosterone in their feces," said Blyton.
"Virus load likely weakens the immune system, so those with a higher KoRV load are more at risk of diseases such as chlamydia which can cause blindness, infertility and death.”
The study involved 67 koalas, including wild individuals receiving treatment for chlamydia before release, others participating in a vaccine trial, and a few kept in captivity due to injury or illness.
The team were able to confirm that the biggest threats faced by koalas of habitat loss and disease are connected. It was an important finding enabling conservationists to understand how to improve support for remaining koala populations.
The study found that the amount of KoRV in each koala stayed about the same over time. Even when a koala was cured of chlamydia, the virus levels didn’t go down.
This means that having high levels of KoRV makes koalas more likely to get chlamydia, rather than chlamydia causing higher virus levels.
"KoRV load could be underpinning the chlamydia epidemic among koalas in northern New South Wales and South East Queensland,” said Blyton.
"When we're looking at koala conservation strategies, we need to be taking a holistic approach because disease and environmental factors are linked.
"The best thing is to preserve good quality habitat and the populations of koalas it supports.
"We are involved in Koala Conservation Australia's breed to release programme, where we are now screening and preferencing animals with low KoRV loads to hopefully give their offspring greater protection against chlamydia and other infectious diseases.”
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Main image: Getty Images
