SeaWorld has just released news that Tilikum, the theme park's resident killer whale performer for the last 23 years, has fallen extremely ill due to what they suspect is a bacterial infection in his lungs, and his vets aren't optimistic about a recovery. A SeaWorld blog post explained the orca's deteriorating health conditions:

We are saddened to report that over the past few weeks, Tilikum's behavior has become increasingly lethargic, and the SeaWorld veterinary and animal care teams are concerned that his health is beginning to deteriorate...

...Despite the best care available, like all aging animals, he battles chronic health issues that are taking a greater toll as he ages.

Our teams are treating him with care and medication for what we believe is a bacterial infection in his lungs. However, the suspected bacteria is very resistant to treatment and a cure for his illness has not been found.

Sources: SeaWorld | Associated Press | People Pets