Koalas (Phascolarctos cinereus) may be one of the world's cuter critters, but that doesn't mean they have it easy. Not only have koala populations become heavily fragmented due to habitat loss, they face numerous threats that they never encountered before: household cats and dogs frequently kill koalas; hundreds die every year after being run over by cars and trucks; and now a deadly virus is spreading to koalas throughout Australia.

The koala retrovirus, which infects and alters the animal's DNA, has been linked to a variety of diseases and medical problems, including leukemia, bone marrow failure, cancer and AIDS-like immune deficiencies. First found in 2000, the retrovirus is already forcing some smaller koala populations into extinction, says Jon Hanger, director of research and ecological services at the Australian Wildlife Hospital. Hanger was the first person to genetically sequence the koala retrovirus after its discovery.

Hanger equates the koala retrovirus with the deadly devil facial tumor disease (DFTD) devastating the world's Tasmanian devils (Sarcophilus harrisii), which many fear may soon drive that species into extinction. He has called for support akin to that given to help protect the devils to stop the spread of the koala retrovirus. "Twenty-two million dollars has been committed by government to manage the contagious cancer afflicting Tasmanian devils. The koala disease epidemic is just as devastating but we know little about it," Hanger recently told Brisbane's Courier–Mail.

Meanwhile, the retrovirus isn't the only illness affecting koala populations. Up to 50 percent of Australia's koalas are infected with chlamydiosis, a disease caused by the chlamydia bacterium, made all the more deadly by the koala retrovirus, which can compromise the animals' immune systems. In fact, one of Australia's most famous koalas recently died of chlamydia: Sam, the koala who became an Internet video sensation after she was rescued from a bushfire by volunteer firefighter Dave Tree earlier this year, passed away on August 5, not from her fire-induced injuries but from chlamydia. (Sam needed to be put to sleep because the infection had ravaged her urinary and reproductive tracts beyond repair.)

Hanger, Tree and others are urging people to donate to Australian Wildlife Hospital through its parent company, Wildlife Warriors Worldwide (founded by television icons, the late Steve Irwin and his wife Terri), to help fund efforts to protect koalas from this virus before it is too late. Scientists at the Queensland University of Technology are also working on a chlamydia vaccine, but say they need to raise around $1.7 million in order to get it out in the next two years.

Image: Koala by Benjamin Turner, via Stock.xchng