Bar worker Sam Thomas has been training for an epic solo 5,000-mile trek across Canada by tackling the jungle — and the snakes — of Guyana.

Mr Thomas, 21, from Kidlington, intends to spend the whole of 2009 hiking the Trans-Canada trail to raise £10,000 to fund research into a brain disease from which his grandmother Maggie Dennison, the former landlady of the King's Head in Wootton, suffers.

To prepare for his Canadian adventure Mr Thomas, who works at The Boat Inn in Thrupp, near Kidlington, flew to southern Guyana where he has been learning how to survive in one of the world's toughest terrains, with the help of an ex-special forces soldier.

He said: "I'm half dead after two of the hardest weeks of my life.

"I was part of a group of six trekkers, plus a leader and two local guides.

"We trekked in virgin jungle, and only five of us made the whole trip."

Mr Thomas carried 30kg of equipment each day.

He said: "We were having to use a lot of energy cutting through the bush — at one stage we covered a pathetic 375m in one hour as the jungle was so thick. Keeping alert to danger was also an issue.

"We were constantly walking through spider webs and having to brush them off before they bit us. And one of the guides found a very toxic snake a few yards from where I'd set my hammock up."

In February, Mr Thomas heads to Vancouver on the west coast before beginning the 5,000-mile journey to New Brunswick on the east coast.

He said: "The aim is to raise cash for research into Progressive Supranuclear Palsy, a degenerative brain disease." His grandmother Mrs Dennison, 73, was diagnosed with PSP in March.

To sponsor Mr Thomas' epic trek, visit www.justgiving.com/samthomas2