Italy captain Fabio Cannavaro has failed a doping test, with his club team Juventus saying Thursday it was the result of cortisone used to treat a bee sting.The Italian Olympic Committee's anti-doping prosecutor, Ettore Torri, opened an investigation.Cannavaro, who helped Italy win the World Cup in Berlin three years ago, was already suspended for the country's World Cup qualifier with Ireland on Saturday due to accumulated yellow cards.