Wild koalas vaccinated against chlamydia in Australia in field trials

NEW SOUTH WALES, Australia — Australian scientists have begun vaccinating wild koalas against chlamydia in an ambitious field trial in New South Wales.

The goal is to test a method of protecting beloved marsupials from a widespread disease that causes blindness, infertility, and death.

“It kills the koalas because they become so sick that they can’t climb trees to find food or escape from predators, and the females can become infertile,” said Samuel Phillips, a microbiologist at the University of the Sunshine Coast who helped develop the the vaccine.

The scientists’ initial goal is to trap, vaccinate and monitor about half the koala population in the Northern Rivers region of New South Wales – which means vaccinating about 50 animals.

Safety and efficacy single dose vaccine, which was developed specifically for koalas, was previously tested by vaccinating several hundred koalas delivered to a wildlife rescue center against other diseases.

Scientists now want to understand the effects of vaccination on wild koala populations. “We want to estimate what percentage of koalas we need to vaccinate to significantly reduce infection and disease,” Phillips said.

The first koalas were caught and vaccinated in March, and the work is expected to last about three months.

Researchers use binoculars to spot koalas in eucalyptus trees, then build circular enclosures around the bases of the trees with doors leading into the cages. Hours or days later, koalas end up climbing down from one tree in search of tasty leaves on another and end up in harmless traps.

“It’s hard to confuse a koala with other animals — they’re pretty easy to spot,” said Jodi Wakeman, veterinary and clinical director of Friends of the Koala, the nonprofit that runs the wildlife hospital where the koalas are brought. vaccination.

After examining the animals to make sure they’re doing well, the researchers administer anesthesia and vaccine injections, then keep them under observation for 24 hours after they wake up to confirm there are no unexpected side effects, Wakeman said.

The goal is to vaccinate healthy koalas to prevent them from contracting chlamydia.

Before release, researchers mark the koalas with a spot of pink paint on their backs to prevent the same animals from being caught twice.

When the first vaccinated koala was returned to its habitat on March 9, scientists placed its cage at the foot of a tree and opened the door. She quickly emerged and jumped up the tree trunk.

Koalas are iconic Australian marsupials, like wombats and kangaroos. They spend most of their time eating and sleeping in eucalyptus trees, and their paws have two opposable thumbs that help them grip and climb trunks.

Australia’s wild koala population has declined dramatically over the past two decades.

In February last year, the Australian federal government declared koalas “endangered” in the eastern regions of New South Wales, Queensland and the Australian Capital Territory.

According to data 2020 assessment from the New South Wales Government.

About half of wild koalas in Queensland are already infected with chlamydia, scientists believe.

When deciding whether to vaccinate, scientists balance the risk of disturbing the animals with the risk of spreading the disease. The trial has been approved by various government bodies, including the Australian Department of Agriculture and the New South Wales Department of Planning and Environment.

The origin of chlamydia in koalas is unconfirmed, but scientists believe that marsupials probably initially contracted the disease through contact with the feces of infected sheep and cattle. It is then sexually transmitted or passed from mother to offspring.

While humans and animals infected with the bacteria that cause chlamydia can be treated with antibiotics, it’s not so easy for koalas.

The “sophisticated” microbes inside the koalas’ stomachs are designed to neutralize toxins in the eucalyptus leaves that are their main food source, said Matthew Crowther, a conservation biologist at the University of Sydney. But their digestive system can also neutralize some drugs, so “that means they don’t respond well to antibiotic treatment,” he said.

Crowther has been monitoring the koala population in northern New South Wales for more than a decade. In 2008, 10% of animals tested there were infected with chlamydia. Today this figure is 80%.

“It was devastating — very, very low birth rates,” he said. “You hardly see any children.”

Other threats facing koalas include habitat destruction from land clearing climate-induced forest fires – can increase stress levels, weaken the immune system and make them more susceptible to diseases, including chlamydia, Crowther said.

Rebecca Johnson, now a principal scientist at the Smithsonian’s National Museum of Natural History in Washington, DC, previously led the Koala Genome Consortium in Australia. She said seeing the effects of the disease up close was worse.

An autopsy of one koala with advanced chlamydia that was euthanized revealed “ovaries completely covered in cysts” and “an intestine full of hard lumps of food, indicating that she was unable to properly digest the food,” Johnson recalled. “She was clearly infertile and in pain.”

There are only a few other examples around the world of scientists attempting to capture and inoculate endangered wildlife for conservation. In 2016, scientists began vaccinating Hawaiian monk seals against a deadly strain of morbillivirus. Two and a half years ago, biologists in Brazil began vaccinating golden lion tamarins against yellow fever.

“Vaccination for wild animals is certainly not routine,” said Jacob Negray, a biologist at Wake Forest University School of Medicine. “But whether it should be used more often is a fundamental question that conservation biologists are now debating.”

The Smithsonian’s Johnson said the benefits to koalas likely outweigh the risks. “Vaccination is an incredibly resource-intensive business. Koalas live high in trees,” she said.

“But since the effects of chlamydia are so debilitating, I think it’s worth it.”

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