A February, 2009, file photo shows firefighter David Tree sharing his water with an injured koala, later nicked named Sam, at Mirboo North after wildfires swept through the region.
Sam the Koala, who won the hearts of the world when video footage of her rescue from Australia's deadly bushfires six months ago hit the Internet, died on Thursday after losing a second battle for survival.
The badly burned koala, filmed drinking from a volunteer fire fighter's water bottle, became a symbol of hope for the survivors of Australia's worst ever bushfires that killed about 173 people and destroyed more than 2,000 dwellings, leaving 7,5000 homeless,
But just months after her rescue from the fires in the state of Victoria, Sam was diagnosed with cysts linked to the life-threatening disease Chlamydia that has ravaged Australia's koala population.
The four-year-old koala was to undergo surgery on Thursday to remove the cysts but John Butler of the Morwell Vet Clinic discovered that Sam had severe changes in her urinary and reproductive tract that were non-operable.
"Unfortunately Sam has been put to sleep. It's very, very sad," Peita Elkhorne of TressCox Lawyers told Reuters on behalf of the Southern Ash Wildlife Shelter.
"It was so severe that there was no possible way to be able to manage her pain."
The debilitating illness Urogenital Chlamydiosis affects 50 per cent of Australia's koala population although it is not known how koalas have come to be infected with the bacterium.