Paula Radcliffe's Olympic history is already a tangled web and so it perhaps comes as no surprise to discover that her latest attempt to exorcise her demons by exercising her ailing body was almost derailed by a spider.

The woman who was Great Britain's best bet for an athletics gold until she suffered a low-grade stress fracture of her left femur in May flew into the team's training camp in Macau and admitted that things had gone from bad to worse. While confirming that she will compete in the Olympic marathon unless her leg breaks down before the event takes place in 12 days' time, Radcliffe's capacity for drama was laid bare.

“Three weeks ago, I got bitten by a spider and had to be rushed into emergency,” she said. “I couldn't walk on my foot for two days. It was poisonous and I had a really bad fever that night. I woke up and couldn't stand on the foot. By the morning it was like a balloon and I had a red line all the way up the inside of my leg.

“I was thinking that somebody somewhere had a little doll and was sticking pins in it. I've lost all the skin and have still got scabs on the toe. There have been points where I thought, "Am I going to make it?'”

Those who wish Radcliffe well will be dismayed but scarcely shocked to hear that she lost a further four days of training in Font Romeu, France, because of an insect many deem to be lucky. Radcliffe does not do middle ground, the highs of setting the world marathon record in 2002 and 2003 tempered by the crushing low of exiting the 2004 Olympic marathon in tears.

Given that she has done little mileage outdoors - she has largely been cross-training and running on treadmills - there are still those who believe that her past Olympic failings are driving her towards another mental and physical meltdown.

“I'm the type of person that if you say I can't do this, then it makes me more determined,” she said. “But, aside from what happened four years ago, it's just been one nightmare after another. When each one comes it hits you like a punch in the stomach and you're down on the floor. But fighting it gives you a bit of energy as well.”

Radcliffe claimed that her build-up to the Olympics had been easier than in 2004, when things went wrong close to the Athens Games. “I was in really good shape and, suddenly, it all dropped on me two weeks before,” she said of the leg injury and then the reaction to the anti-inflammatory drugs she took. “This time I think I've had the worst of the stress.”

Gary Lough, her husband and coach, was palpably unimpressed by the number of photographers and cameramen waiting for Radcliffe at her hotel, and said: “There's no definite decision been made.”

When told that Dave Collins, the UK Athletics performance director, had said it would be a “team decision”, Radcliffe added: “I don't think you're getting it. It's not a decision, is it? I don't even want to talk about it. I'm racing unless my leg breaks down and I can't run. That's it. That has already been decided.”

Radcliffe says that she has recovered from similar adversity, bouncing back by winning the London Marathon in 2002 - her first attempt at the distance - three weeks after suffering a knee injury, but this is surely her biggest challenge. She has been going stir-crazy in Font Romeu, running on a treadmill, staring at the same wall, and says that she has “totally knackered” her iPod shuffle.

“My aim is to win the race,” she said. “I wouldn't be here if I didn't think I was in good-enough shape.”

She has not been jogging on the beach yet, but, given her recent form and sightings of rabid dogs, she might be well advised to steer clear.

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Sting in tail: Analysis by Lewis Smith

Experts trying to identify what caused Paula Radcliffe’s foot to swell say it was more likely to be a scorpion’s sting. Plenty of spiders are found in the Pyrenees, where Radcliffe lives, but they are too small to harm humans. Scorpions are found there and David Bohan, of Rothamsted Research, said that they make better suspects, especially as spiders “often get the blame”.

Two scoprions in the region with the capacity to sting humans are Belisarius xambeui and Euscorpius flavicaudis, both of which like to lurk under stones and in old buildings, and even as adults are little more than an inch long.

“We don’t know of any spiders that might be able to do this,” he said after consulting colleagues. “We think it’s more likely to be a scorpion - even so, it’s still a bit of a long shot.”