Koalas die of chlamydia, climate change is making matters worse
A silent killer is spreading through Australia’s koala population, posing a threat that wildlife experts say could wipe out the iconic marsupial in large parts of the country.
The culprit is chlamydia, a sexually transmitted bacteria that infects over 100 million people worldwide each year and can cause infertility in men if left untreated.
For koalas, uncontrolled chlamydia can cause blindness and painful cysts in an animal’s reproductive tract that can lead to infertility or even death.
Worse yet, the antibiotics used to treat the disease can destroy the delicate gut flora that koalas need to consume their staple diet of eucalyptus leaves, causing some to starve even after being cured.
The disease can also spread quickly.
In 2008, there was a “very, very low prevalence of chlamydia” – around 10% – in the koala population in Gunnedah, a rural town in northeastern New South Wales, according to Mark Krockenberger, professor of veterinary pathology at the University of Sydney.
By 2015, this figure had risen to 60%. Today, about 85% of that koala population is infected with the disease, Krockenberger said.
“If you think about it, this is no longer a viable population due to infertility. Almost all females infected with chlamydia become infertile within a year, maybe two years at most… Even if they survive, they do not. not reproduce, ”he said.
Experts say situations like Gunnedah are occurring among koala populations across Australia, threatening populations already vulnerable to worsening bushfires and habitat loss from deforestation.
Scientists are now testing chlamydia vaccines to protect animals.
“We are at a very high risk if this vaccine strategy does not work… localized extinctions,” Krockenberger said.
Are koalas endangered in Australia?
There are few Australian animals more iconic than the koala.
The gray, fluffy-eared marsupial, which eats eucalyptus leaves and carries its young in its pouch, is only found in Australia and is regularly seen in the country’s cultural representations.
But koalas face a number of threats to their survival. Besides disease, marsupials experience habitat loss and are often attacked by feral dogs and struck by cars.
The koala is listed as “vulnerable” on the Red List of the International Union for the Conservation of Nature (IUCN), which lists species threatened with extinction. IUCN says there are between 100,000 and half a million koalas in the wild, but the Australian Koala Foundation says the number is closer to 58,000.
Confusion over the size of the koala population in Australia prompted the government to commit A $ 2 million ($ 1.47 million) last year to a national census of koalas to determine where they are and how much they are. remains.
The country’s koala population suffered heavy losses in the catastrophic 2019 bushfires, which destroyed more than 12 million acres (48,000 square kilometers) of land across New South Wales alone.
The fires have killed or displaced nearly 3 billion animals, according to the World Wide Fund for Nature (WWF). This figure includes more than 60,000 koalas who died, lost their habitat or suffered injuries, trauma, smoke inhalation and heat stress from the flames.
In mid-2021, an Australian government report on the conservation status of koalas recommended that the animal’s status be changed to ‘endangered’ in Queensland, New South Wales and the South Wales. Australian capital, due to the rapid decline of the population in these areas. In some areas, the report found that populations had almost halved in just 20 years.
The Australian government is developing a national stimulus package for the koala bear that will be reviewed in December 2021 before potentially becoming law in 2022.
But Deborah Tabart, president of the Australian Koala Foundation, says much more needs to be done to protect koalas and their habitat across the country, warning that marsupials could be wiped out within three generations.
“We want a law to protect koalas,” she said. “If you really want to protect this species, you would have effective legislation and that means protecting the trees,” she said.
Activists say it would be akin to the Bald Eagle Act in the United States, which protects the country’s national emblem from threats to its people and habitat.
How is chlamydia spread?
In the face of threats to the koala’s habitat and food supply, chlamydia may appear to be a secondary problem.
But with the numbers dwindling, experts said reproduction has never been more important.
There are two varieties of chlamydia in Australian koalas, one of which, chlamydia pecorum, is almost entirely responsible for the most severe cases of the disease in the population.
An article published in September 2020 in FEMS Microbiology Reviews stated that the most dangerous strain of chlamydia could come from domestic cattle brought to Australia by European colonizers in the 19th century.
The disease spreads in koala populations through reproduction and social behavior related to mating, although joeys – baby koalas – can catch the disease from their mothers.
According to the University of Sydney, infection rates in some koala populations in Queensland, New South Wales and Victoria can reach 100%, making them completely infertile.
Highlighting the life-threatening potential of the disease, a study published in the Journal of Applied Ecology in March 2018 found that of 291 koalas examined over four years, 18% had died of chlamydia or related complications.
The disease was the second leading cause of death, after animal attacks.
Climate change is making the problem worse
The climate crisis has made Australia more vulnerable to devastating bushfires, such as those seen in 2019, as well as drought and heat waves. It also makes koalas more susceptible to disease.
According to Australia’s leading scientific body, the Commonwealth Scientific and Industrial Research Organization (CSIRO), the country has already warmed by about 1.44 degrees on average since 1910.
The Australian government report says that when marsupials are exposed to unusually stressful environmental conditions, including “hot weather, drought, habitat loss and fragmentation,” chlamydia spreads faster in their populations.
Experts say they have witnessed similar rapid outbreaks of disease in nature. Krockenberger said in his Gunnedah population sample, a series of heat waves and droughts in 2009 and 2010 preceded a doubling of chlamydia cases.
Peter Timms, professor of microbiology at the University of Sunshine Coast in Australia, said that once koalas’ stress hormones increase due to environmental issues, infections often progress from a relatively minor problem to “a problem. worse”.
He said a combination of habitat loss and climate change was causing koalas “chronic stress”, depressing their immune systems.
“All of this leads to a poor response to chlamydia. It turns them from low grade chlamydia infections to more serious illness,” he said.
“We are doing it to them. And we are doing it on all fronts.”
Chlamydia vaccine trials for koalas
But help may be on the way for Australia’s koalas.
A chlamydia vaccine, developed by researcher Timms over the past decade, is currently being tested among the country’s koala population to protect animals against serious infections.
Control trials are underway to test the vaccine’s effectiveness on small groups of koalas – often around 20 or 30 at a time, Timms said. The current trial is the largest to date, involving 400 koalas.
Some koalas are vaccinated when brought to veterinary hospitals with complaints other than chlamydia, while others are given the vaccine as part of coexisting conservation efforts, he added.
“We know the vaccine can reduce the rate of infection,” Timms said. “It doesn’t reduce it to zero. There are no vaccines that do, but it does take the infection load off down.”
He said that while it is hoped that the process will reduce the rate of infection, it is difficult to monitor the spread of chlamydia in a wild population.
Krockenberger of the University of Sydney, who is participating in a separate vaccine trial, said the purpose of the drug was not to reverse disease progression in individual koalas. “Once they are chronically infected they are often able to live reasonably happily, they just cannot reproduce,” he said.
He said that instead, the hope is that by reducing levels of infectivity in koalas with chlamydia, researchers can prevent the disease from spreading to new hosts and thus maintain a breeding population.
“We also hope that unaffected animals, when vaccinated, will be more resistant to infection,” he said.
Timms said once the vaccine is found to be safe and effective, he hopes to roll it out to wildlife hospitals in Australia to vaccinate all the koalas that come through their doors.
He said people often ask him how he’s going to vaccinate “the last koala in the last tree” against chlamydia, to which Timms replies that he “isn’t even going to try.” All he can do is try to save as many people as possible.
After all, “they are wild animals,” he said.