Affected by habitat (栖居地) loss and climate change，like many other unique Australian animals，koalas are being squeezed into smaller regions.But at present，it is a deadly disease，a somewhat silent killer that causes a further decline in the koala population，that is worrying many scientists about the fate of the koala.

　　The killer is Chlamydia，which has caused symptoms in up to 50 percent of the wild koalas，with probably even more infected (感染) but not showing symptoms.It has been particularly severe in Queensland，where nearly all koalas are infected.The disease causes many symptoms including eye infections，which can lead to blindness，making it difficult for them to find their primary food.

　　Treating Chlamydia in wild koalas is a challenge.There is no treatment available for it．Only a small percentage of the animals can be treated successfully and returned to the wild.Besides，there is no national plan in Australia to save the koala；it is up to each region to make management plans for its koala population.

　　The good news is that researchers are working to test a vaccine (疫苗) that would help prevent further spread.If all goes well，plans can be carried out to distribute the vaccine more widely.But it's impossible to vaccinate all wild koalas.

　　Another possibility would be to make vaccine distribution a routine part of treatment for the thousands of koalas brought into care centers every year after they are injured by cars or dogs.

　　While it is a combination of problems that are affecting the wild koala population，many experts believe this vaccine would be an important step in helping koalas survive longer.It may buy enough time to give researchers a chance to solve some of the other problems facing Australia's koalas.

　　【语篇解读】　本文主要介绍澳大利亚的珍贵动物之一考拉现在处于困境之中。

　　1．Which isn't considered the main cause of koala's population decline?

　　A．A deadly disease.

　　B．Injuries from cars and dogs.

　　C．Climate change.

D．Habitat loss.