The world loved Knut the polar bear. People followed his life on YouTube, bought stuffed animals in his likeness, and someone even wrote a song in his honor.
When he died unexpectedly at the Berlin Zoo after a short and rather tragic life, the world then mourned Knut as scientists failed to fully explain how the polar bear died at only 4-years-old. In captivity, a polar bear can live to be 30, the Smithsonian noted.
Four years after the shocking death, scientists finally have the answer, and it’s a bit confounding. The animal succumbed to a human disease, anti-NMDA receptor encephalitis, which caused his immune system to attack the nerve cells in his brain.
There were some signs that Knut suffered from this condition; he demonstrated similar symptoms to those expressed by human sufferers, just before he died. In March 2011, he started to spin around in circles, then lost control of a trembling back leg. Then he had a seizure, collapsed, and fell into a pool in his enclosure. As visitors watched, the animal drowned.
But even if the polar bear hadn’t drowned, the illness had progressed so far it would’ve killed him eventually.
Right after Knut passed, scientists removed some tissue for examination and found the disease right away. What confused them was the fact he didn’t have a virus, yet his immune cells made it look as though he did, Live Science explained.
Enter neurologist Harald Prüss. He read the polar bear’s death report and saw some similarities between his illness and one he’d seen his human patients display before: the rare anti-NMDA receptor encephalitis. The symptoms in people start with fever, headaches, and psychosis, then if left untreated, moves on to motor problems, seizures, and death.
The disease causes immune cells to attack certain nerve cells in the brain, making them break down. In people, a case of influenza or herpes can be the culprit, but no one yet knows what triggered Knut’s illness.
This finding is significant because the polar bear is the first animal ever found to have suffered from this condition and could mean that it’s more common in animals than scientists previously thought. In the future, zoo animals and endangered species could get critical treatment, including antivirals, antibiotics, and immune-suppressing drugs. Because animals can’t warn vets of the early symptoms, such meds could only be administered once they show outward signs in the final stages.
It seems fitting that Knut would be the first animal to die of this human disease. His life story was already incredibly dramatic: His mother abandoned him and brother died, leaving him to be raised by a human family at the zoo. Zookeeper Thomas Dörflein formed a bond with him, bottle-feeding, snuggling, and swimming with the animal. Dörflein then died in 2008, leaving him alone in the world again.
As an adult, he had trouble with his peers — he was turned down by the females and fought with the males. Now, at least, it seems his tortured life will do some good in the animal kingdom.
[Photos Courtesy Sean Gallup, Andreas Rentz/Getty Images]