SACRAMENTO, JUNE 9 -- Antitax crusader Paul Gann held a news conference today to announce that he has AIDS and will spend the rest of his life campaigning to keep others "from falling under this deadly spell."

Gann, 74, says he contracted the disease during open-heart surgery five years ago. With Howard Jarvis, who died last year at 84, he sponsored the 1978 campaign for Proposition 13, which cut California property taxes by $7 billion and triggered tax-cutting nationwide.

"I'm here to start what may become the last campaign of my life," said Gann, who appeared with his wife of 55 years, Nell. "I don't know how much more time I have but I want to spend it to protect others from falling under this deadly spell.

". . . The only way to control it now is to find out who has it and let others know. I'm for testing for everyone and telling everyone." He said he particularly advocates testing of immigrants and those seeking marriage licenses.

Gann, a former U.S. Senate candidate, is the most prominent political figure in California to acknowledge contracting acquired immune deficiency syndrome, which robs the body of its ability to resist infection.

Gann's doctor, Dennis Ostrem, said it had not been confirmed that Gann received contaminated blood during his 1982 surgery but that donors of the blood were being traced and asked to volunteer for testing. Ostrem said Gann has AIDS-related complex (ARC), a precursor to the disease.

Routine screening of blood donors for the AIDS virus began in 1985. Nationally and in California, about 2 percent of AIDS cases have been documented to have come from blood transfusions.