Thinking about factors that tend to cause animal extinction, from deforestation to climate change, the plight of the koala's might be a little more surprising. Among other problems, they're being threatened by chlamydia.
In the last 10 years, koala populations have dropped by about 80 percent, according to a report by the BBC, and in 2012, the Australian government placed them on an endangered animal list.
Koala chlamydia (a different strain from the human kind) can lead to blindness and infertility in koalas, which worsens their population declines.
Scientists in Australia are working on a solution: developing a vaccine. In a five year trial, researchers observed 30 vaccinated koalas and compared them to 30 un-vaccinated koalas. They found that that vaccinated koalas, even the ones who were already infected with chlamydia, did much better than the un-vaccinated koalas. The vaccine even seemed to lessen the symptoms for infected koalas.
The vaccine would be a much better alternative to the current mode of treatment: antibiotic treatments. Koalas are captured and held in captivity for months in overworked animal hospitals. These centers can't always keep up with all the koalas that need attention and many koalas are so sick, they have to be put down.
While the chlamydia vaccine seems very promising, there are other factors which are killing off koalas which also need to be addressed. Many get hit by cars or chased by dogs and expanding cities are pushing them out of their homes. Koalas are also plagued by an HIV-like virus which can go straight into koala sperm and eggs, making it hard to prevent infection.
But the chlamydia vaccine is a start.
"It's all very promising and it's not just that it's doing the right thing from an immune response point of view, but it's actually protecting a significant number of them out in the wild climbing around trees," Professor Peter Timms, one of the lead researchers, told Agence France Presse. "The vaccine would actually make a difference."