PARIS (Reuters) – An ailing killer whale adrift in France’s River Seine will be euthanised after a plan to guide it back to sea failed and scientists concluded it was in agonising pain and terminally ill, the local prefecture said on Sunday. The 4-metre (13-foot) orca, identified as a male, was first spotted at the mouth of the Seine on May 16 between the port of Le Havre and the town of Honfleur in Normandy, before it swam dozens of miles upstream to reach west of the city of Rouen. Following a meeting with national and international scientists, including marine mammal specialists, the local …