Sydney  - Sam the koala, made famous by taking a drink of water from a firefighter after surviving Australia's worst-ever bush blazes, was put down Thursday after being diagnosed with the sexually transmitted disease chlamydia.

Heart-warming pictures of Sam flashed around the world in February at the height of forest fires north of Melbourne that killed 173 people, destroyed over 1,800 houses and left 7,500 people homeless.

Sam, 4, was taken into care after she was pictured drinking from a water bottle held by Good Samaritan firefighter Dave Tree. The video of their touching encounter sparked worldwide concern for the millions of animals that perished or were injured in the conflagration.

"I could see she had sore feet and was in trouble, so I pulled over the fire truck," Tree explained at the time. "She just plonked herself down as if to say 'I'm beat.' I offered her a drink and she drank three bottles."

Sam, who suffered severe burns to her paws in the fires, developed ovarian cysts through catching chlamydia, a common affliction in koalas.

Peita Elkhorne, a spokeswoman at the Southern Ash Wildlife Shelter, said the infection was "so severe that there was no possible way to be able to manage her pain."

Prime Minister Kevin Rudd paid tribute to Sam, saying she had become a national hero and an embodiment of the national spirit.

"I think that gave people of the world a great sense that this country Australia could come through those fires," Rudd said. "Sam the koala was part of the symbolism of that and it's tragic Sam the koala is no longer with us." (dpa)