By Alasdair Fotheringham
BUSSETO, Italy (Reuters) - Defending Giro d'Italia champion Ryder Hesjedal has withdrawn from this year's race, the Canadian's Garmin-Sharp team announced before the start of Friday's stage 13.
Hesjedal had slipped to 38th place after 12 stages, 32 minutes and 55 seconds down on overall leader Vincenzo Nibali of Italy after suffering badly in the first mountain stages of the race last weekend.
"It's heartbreaking," Hesjedal said in a news release.
"I want to be here for my team and for all the people who have supported me to get me here to this point.
"I built my entire season around the Giro and I came here feeling great, but I have been suffering since the (stage eight) TT (individual time trial).
"We're working on it but we're not sure what's wrong. There's a virus that's been going around, so it could be that, or severe allergies."
Hesjedal became his country's first Giro d'Italia winner when he edged out Spain's Joaquim Rodriguez by 16 seconds after a ferocious two-week duel through the mountains, with the Canadian gaining the upper hand on the final day's time trial in Milan.
Hesjedal's withdrawal follows that of France national champion Nacer Bouhanni, who announced on Thursday evening that he was quitting the 21-stage race.
Bradley Wiggins's continuing presence in the race will be decided later on Friday after the ailing Team Sky leader lost more time on Thursday, leaving the British Tour de France winner more than five minutes adrift of Nibali in 13th place.
Friday's 254-km stage favors the sprinters and runs from Busseto to Cherasco with this year's race finishing in Brescia on May 26.
(Editing by John O'Brien)