In March of 2007, an adorable polar bear named Knut made his debut at the Berlin Zoo in Germany and instantly became the star attraction of the zoo. Born Dec. 5, 2006, to a former circus performer from East Germany, 20-year-old Tosca, and her 13-year-old mate Lars, originally from Tierpark Hellabrunn in Munich, the cub and his unnamed brother were rejected by Tosca and abandoned on a rock in the polar bear enclosure.
The brother died, but Knut became a worldwide star until he died four years later at a very young age.
Polar bears can survive for 20 years in the wild and can sometimes live even longer in captivity, but on March 19, 2011, hundreds of Berlin Zoo visitors watched the 4-year-old Knut drown after suffering from seizure and collapsing into his enclosure's pool. The polar bear died of encephalitis of unknown etiology, which remained a mystery for a long time.
Researchers from Germany have finally found the cause of Knut's death and this discovery may also shed light on a condition that affects humans, too.
Immediately after the drowning incident, scientists performed a necropsy and found that the polar bear suffered from a swelling of the brain. They initially thought the infection was caused by an inflammation, but disproved that theory later.
"At the beginning of 2014, we had basically exhausted every option," said Alex Greenwood from the Leibniz Institute for Zoo and Wildlife Research, which led majority of the investigation into Knut's untimely death. According to Greenwood, they actually thought it might take decades to crack the case, so they shelved samples for the investigation until a call from a German neurologist later brought them closer to solving the mystery.
Dr. Harald Pruess, a neurologist from the Charite Hospital in Berlin and a researcher from the German Center for Neurodegenerative Diseases, said he observed similarities between Knut's case and those of his human patients suffering from anti-NMDA receptor encephalitis. This is a noninfectious autoimmune disease where the body gets attacked by its own brain cells, and it was discovered just eight years ago and had been found thus far only in humans.
According to Greenwood, it took them only about six to eight weeks before actually confirming that the cause of Knut's death was "really was that."
Greenwood added that had Knut's keepers known what the polar bear was suffering from, and had he not fallen into the water, Berlin Zoo's star attraction might have survived. Humans with the condition are given cortisone, a drug that suppresses the immune system, until the body recovers and in most cases they can return to a normal life.
Further details into the team's investigation and findings were published online on Aug. 27 in the journal Nature Scientific Reports.
