[Reading Science] Endangered Koalas with STDs... Can Vaccines Save Them?

Pilot Vaccination Begins in New South Wales, Australia
Population Plummets Due to Wildfires, Land Clearing, and Epidemics
Australian Government Declared Endangered Status in February Last Year

Australian scientists have begun vaccinating koalas, an endangered protected species, against the spread of sexually transmitted infections. However, it has been revealed that they are facing great difficulties as koalas live high up in trees and are sensitive, making them hard to capture.

According to the Associated Press on the 10th (local time), Australian scientists recently started vaccinating wild koalas living in the New South Wales region against chlamydia, a type of sexually transmitted infection. The first koala was captured and vaccinated in March, and the work is expected to continue for the next three months. The goal is to capture and vaccinate about 50 wild koalas, roughly half of those living in the Northern Rivers area of New South Wales, and monitor their condition.

Koalas Resistant to Antibiotics

Chlamydia is a type of sexually transmitted infection commonly found in humans and livestock. It spreads through mating or from mother to offspring. While humans and livestock can be treated with antibiotics, koalas are different. It is a fatal infectious disease that can cause blindness, infertility, and even death. Professor Matthew Crowther of the University of Sydney explained, "The microorganisms in the koala's gut neutralize the toxins in eucalyptus leaves," adding, "The problem is that because of the influence of these microorganisms that neutralize the toxins, koalas do not respond well to antibiotic treatment."

Koalas are marsupials and, along with wombats and kangaroos, symbolize Australia's well-preserved wilderness. However, their numbers have drastically declined over the past 20 years. In February, the Australian federal government officially designated koalas as an endangered species. It declared that koalas are at risk of extinction in regions such as eastern New South Wales, Queensland, and Melbourne. The New South Wales government also announced in 2020 that koalas could become extinct by 2050 due to infectious diseases, habitat destruction, and roadkill. In particular, chlamydia, a type of sexually transmitted infection commonly found in humans, is a major cause of the decline in koala populations. About half of the wild koalas living in Queensland are infected, and in New South Wales, the infection rate has soared from 10% in 2008 to 80% currently. Professor Samuel Phillips of the University of the Sunshine Coast said, "When infected with chlamydia, koalas cannot climb trees to find food or escape predators, and females cannot become pregnant," adding, "It is a disease that drives koalas to death."

[Image source=Yonhap News]

80% Infection Rate Accelerates Extinction Risk

Accordingly, Australian scientists have begun developing and administering vaccines to protect the koala population. This vaccine is a single-dose and specifically designed for koalas. Prior to this pilot vaccination, it was tested on other koalas housed in wildlife rescue centers. Professor Phillips said, "Our goal is to determine the proportion of koalas that need to be vaccinated to significantly reduce (chlamydia) infection."

However, scientists are struggling with the vaccination process. Since koalas live high in trees and are cautious, special methods have been devised to lure and capture them. First, researchers use binoculars to locate koalas in eucalyptus trees, then build a circular enclosure with a door around the base of the tree. After some time, when the koala finishes eating the food in the tree and comes down to move elsewhere, it is guided into the enclosure made by the research team. The captured koala is then safely examined for health, administered anesthesia and the vaccine, and observed for side effects for 24 hours before being released. To prevent the same koala from being captured and vaccinated again, pink dye is applied to its back.

The exact route by which koalas contracted this human sexually transmitted infection is still unknown. However, it is suggested that exposure to the feces of sheep or cattle raised by humans may have infected the koalas.

In addition to this, Australian koalas face threats to their survival due to habitat loss caused by human deforestation and wildfires linked to climate change. On top of that, increased stress weakens their immune systems, making them more vulnerable to the spreading chlamydia.

Scientists worldwide are paying attention to this koala case. Forced vaccination of wild animals has only been done twice before: in 2016 in the United States to protect Hawaiian monk seals from the deadly morbillivirus, and at the end of 2021 in Brazil to vaccinate golden lion tamarins against yellow fever. Professor Jacob Negrey of Wake Forest School of Medicine said, "Vaccination of wild animals is not yet a commonly practiced measure," adding, "There is currently a fundamental debate among biologists about whether such measures should be used more frequently." On the other hand, Rebecca Johnson, senior researcher at the Smithsonian National Museum of Natural History, pointed out, "Because koalas live high up in trees, vaccination requires a lot of effort and resources," but added, "However, the impact of chlamydia is so severe that vaccinating them is definitely worthwhile."