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What killed Knut? Riddle of polar bear’s death solved

FILE - In this Dec. 5, 2007 file picture polar bear Knut  walks in the enclosure during  the celebration of his first birthday in the Zoo Berlin.  Scientists in Germany say they have finally figured out what killed Knut the polar bear four years ago. Knut drowned after swelling of his brain caused him to collapse and fall into his enclosure's pool at Berlin Zoo. In an article published Thursday Aug. 27, 2015  by the journal Nature Scientific Reports, researchers say Knut suffered from anti-NMDA receptor encephalitis.  (AP Photo/Markus Schreiber,file)
FILE - In this Dec. 5, 2007 file picture polar bear Knut walks in the enclosure during the celebration of his first birthday in the Zoo Berlin. Scientists in Germany say they have finally figured out what killed Knut the polar bear four years ago. Knut drowned after swelling of his brain caused him to collapse and fall into his enclosure's pool at Berlin Zoo. In an article published Thursday Aug. 27, 2015 by the journal Nature Scientific Reports, researchers say Knut suffered from anti-NMDA receptor encephalitis. (AP Photo/Markus Schreiber,file) FILE - In this Dec. 5, 2007 file picture polar bear Knut walks in the enclosure during the celebration of his first birthday in the Zoo Berlin. Scientists in Germany say they have finally figured out what killed Knut the polar bear four years ago. Knut drowned after swelling of his brain caused him to collapse and fall into his enclosure's pool at Berlin Zoo. In an article published Thursday Aug. 27, 2015 by the journal Nature Scientific Reports, researchers say Knut suffered from anti-NMDA receptor encephalitis. (AP Photo/Markus Schreiber,file)

BERLIN (AP) – Scientists in Germany say they have finally figured out what killed Knut, the polar bear who was a worldwide celebrity.

Knut drowned four years ago after swelling of his brain caused him to collapse and fall into his enclosure’s pool at Berlin Zoo.

In an article published Thursday by the journal Nature Scientific Reports, researchers say Knut suffered from anti-NMDA receptor encephalitis. That’s an autoimmune disease discovered in humans eight years ago and never previously found in animals.

Alex Greenwood of the Leibniz Institute for Zoo and Wildlife Research says the discovery paves the way for treatment of other animals with the disease.

He says the case may also help raise awareness of what he called “Knut’s disease” and ensure early treatment for the one in 200,000 people affected annually.