WHAT a difference 12 months can make.

This time last year Chris Froome was almost out of contract at Team Sky and, as the transfer buzz centred around what would happen to the riders at the now defunct HTC-Highroad – not least the future of golden boy Mark Cavendish – his plight went largely ignored.

Then came that stellar performance at the Vuelta a Espana last September. Drafted in as a domestique to Sky team-leader Bradley Wiggins, Froome came within a whisker of taking his first Grand Tour win, finishing second to Juan Jose Cobo by just 13 seconds.

Froome went from barely a blip on the cycling radar to one of the most sought after names in the sport. Indeed, had Sky renewed his contract before the Vuelta, they could have got him for a fraction of the king's ransom the Kenyan-born British national can now demand.

But his meteoric rise from zero to hero has raised eyebrows. Some detractors believe Froome's new-found success to be a little too good to be true – testament to cycling's enduring wink, wink, nudge, nudge culture when it comes to doping. Froome, however, asserts a much more mundane reason: finally being diagnosed with the waterborne parasitic disease bilharzia, which he has been fighting for the past three seasons.

The pathogen, transferred by microscopic snail larvae and believed to have entered his system during a trip home to Africa, has impacted heavily on his career. After making his Tour de France debut in 2008 with Barloworld, where he finished 84th, he all but disappeared from the cycling scene as he struggled with fatigue.

Doctors initially diagnosed mononucleosis, but the treatments failed. It was only after Froome underwent extensive blood screening following his switch to Sky in 2010 that the parasitic infection was caught and he was prescribed an eye-wateringly strong treatment, similar to chemotherapy.

The start to his 2012 season was also marred by the condition. After withdrawing from the Volta ao Algarve with a severe chest infection, blood tests showed the bilharzia parasites had returned. At one stage it was doubtful if the 27-year-old rider would even make this year's Tour de France.

So who is Chris Froome? The man himself paints a colourful picture of a life growing up in Africa's wilds, spending his childhood fishing in the bush and out-running angry hippos.

Having started his cycling career in mountain biking, Froome began road racing in South Africa in his teens, specialising as a climber. Born at 6000ft altitude, many credit this for his apparently colossal lung capacity on the Tour's punishing climbs.

His race debut in Europe wasn't without incident after he crashed into a marshal at the 2006 Under-23 World Time Trial Championships in Salzburg. "I remember in the route recon, we didn't look at the first 100 metres off the start ramp," he recounted to Cycling Weekly. "It looked different with the road all cordoned off, and I ended up hitting him. I saw him a couple of days later, his chest and ribs were black with bruises. He wasn't too impressed. That was a good arrival to European racing."

As the Tour de France rolls ever closer to Paris – and an increasingly more certain podium place – the more pertinent question is perhaps: what now for Froome?

There have already been murmurings that he may not see out his three-year contract at Sky. The Twittersphere has been abuzz with comments from disgruntled fans who suggest that Froome is getting a little too big for his boots. "Good luck playing second fiddle to Mark Renshaw at Rabobank next year," wrote one.

Froome, to his credit, seems to have indicated that he intends to stay with Sky, albeit with some lofty expectations. The rider has said that, having loyally supported Wiggins' aspirations on the road to Paris, he hopes to have similar faith shown in his own abilities when the 2013 Tour de France route is announced this autumn.

Froome said: "It all depends on the route. If there are Cols I hope Sky will be honest and all my team-mates will be at my service, with the same loyalty I have shown today."

Certainly, Froome has the Olympics to look forward to, although it is likely he will find himself playing second fiddle to Wiggins once again. Not this time on team orders, but on the basis that few in the world are able to match Wiggins' time trial prowess.

Then an exciting Vuelta a Espana beckons as the formidable Alberto Contador returns from serving a backdated two-year suspension for a positive drug test and will surely relish the challenge of a head-to-head with Froome.

What is clear is that, long after rumours of rivalries and internal tension between he and Wiggins are consigned to the vaults of Tour de France legend alongside those of Greg LeMond and Bernard Hinault before, Froome's story still has much more to unfold.

* Luxembourg's Frank Schleck is out of the Tour de France after failing a doping test, a spokesman for his RadioShack-Nissan team said. Earlier, the International Cycling Union (UCI) announced that the rider had tested positive for the diuretic Xipamide. Schleck is the older brother of Andy, who won the 2010 Tour after original winner Alberto Contador was stripped of the title for doping offences.