"They have tried to kill me off so many times," Castro told scores of student leaders who gathered to mark the start of the 79-year-old president's studies at the University of Havana 60 years ago.
But, Castro said, "disappointment follows disappointment," for those who believe and circulate the frequent reports that his health is suffering.
Dressed in his trademark olive green uniform, the communist leader looked fit and actually seemed to gain strength as he stood at a mahogany lectern inside the university's elegant Aula Magna during a speech that stretched over more than 3 1/2 hours.
Castro told the students that he exercises regularly, watches his diet, "and don't neglect myself in anyway."
"And now they say that the CIA has discovered I have Parkinson's!" he told the student leaders at his alma mater, where he studied law before he launched the revolution that triumphed on Jan. 1, 1959.
Countless rumors have circulated about Castro's health over the years, especially as he has grown older, and they have been regularly dismissed by Cuban authorities. The reports about Parkinson's have been around for at least seven years. He also has been reported to have suffered from everything from strokes to cancer.
The latest report about Castro's health emerged Wednesday when U.S. officials said that American intelligence analysis indicates that he may suffer from Parkinson's disease. The report was first carried by The Miami Herald.
The obsession with the Cuban leader's health is especially profound in South Florida, home to hundreds of thousands of anti-Castro exiles who dream of a different country after their nemesis dies. Castro, who turns 80 next August, has ruled the island for nearly 47 years.
Interest in his health was piqued last year when he suffered an accidental fall on a concrete step leaving a speech, causing him to shatter a kneecap and breaking an arm. His health was also in focus in 2001, when he suffered a fainting spell during a speech outdoors under a searing tropical sun.
Castro's designated successor has long been his younger brother, 74-year-old Defense Minister Raul Castro.
Castro and other Cuban officials insist "there will be no transition" and that the island's socialist political and economic systems will live on long after he is gone, reported AP. P.T.