Jose Augustin Lopez's wheelchair is in a pitiful state. When he comes to a hill, his son Jefferson Alexis has to push. They have another 500 kilometers to go on this arduous odyssey from their home in Venezuela towards Colombia's capital Bogota.

Lopez is in need of vital medical treatment that he cannot get at home because of a lack of antibiotics and bandages.

Venezuela's economic crisis has left shortages of basic necessities, food and medicines, and Lopez couldn't wait any longer, he was convinced he would die if he did.

"I had to take the road to Colombia to get all the medicines I need and some sustenance to take home," the 52-year-old told AFP.

He has been confined to a wheelchair for the last 13 years following a road accident that left him without feeling in his legs.

But he has spent so much time sitting in his wheelchair that he developed sores that subsequently infected his anus and rectum.

Doctors performed a colostomy so he wouldn't become poisoned by his own excrement, but he's had no post-surgical treatment since.

"If I had stayed there, I think I was dead because I would have contaminated myself," said Lopez, who has covered his open wounds with plastic shopping bags and industrial tape.

And so father and son set out on the road to salvation, like many other Venezuelans fleeing poverty and hardship in a country suffering a fourth year of recession, where the currency is worth almost nothing due to hyperinflation the International Monetary Fund expects to reach one million percent this year.

Already, 1.6 million people have left since 2015, according to the United Nations.

- 'A good sacrifice' -

Jefferson Alexis pushes his father's chair when the gradient rises and holds on tightly when they come down the other side.

They have endured the severe cold and heat that accompany such changes in topography.

"You have to make a good sacrifice to have a good future in life," said Jefferson Alexis, 25, who gave up his mechanical engineering studies to accompany his father.

"Together with my father we'll cross the whole of Colombia if we have to!"

Penniless, they set out around a week ago from San Cristobal, the capital of the western state of Tachira, but the progress has been slow. It took them three days to cover a distance other migrants manage in a matter of hours on foot, or by hitchhiking if they're lucky.

"It's been a demonstration of love," Lopez says of his son.

They have spent nights out in the open on dark Colombian roads, their blankets and mattresses soaked by rain, fearful of attacks or bites from snakes lurking in the bushes.

Some local good samaritans have given them food and blankets, but they eat by the side of the road, enduring the risks that entails as motorbikes, cars and trucks hurtle past.

Venezuela's economic woes, sparked by a crash in the price of oil, on which the country is almost entirely dependent, hit Lopez hard after his accident.

He lost his job as a courier in San Cristobal and tried to make ends meet selling lottery tickets to neighbors and acquaintances.

But that wasn't enough to support his mother, wife and three children, so other family members helped out where they could.

"Now, you can't play the lottery, there's no more help, no-one helps anyone else," sighed Lopez.

- 'Totally exhausted' -

In Colombia, though, he expects to get "help with the wheelchair, which is what I need most."

Trudging along under a punishing sun, Lopez and his son approach Pamplona, just over 100-kilometers (60 miles) into their journey, with five times that still to come.

More than a million Venezuelans have entered Colombia since the economic crisis broke out in 2014 with the oil price crash. Many head on to Ecuador, Peru and Chile, or even further afield. Their swollen feet often bear witness to long journeys embarked upon.

"I'm totally exhausted and the (wheelchair) seat is on its last legs, too. When it's not one thing, it's another. But, on we go," said Lopez, who come rain or shine never removes his black wooly hat.

With every step, Jefferson Alexis is finding it harder to push the chair. The rubber on the tires is wearing thin and the wheels barely turn.

The Bogota utopia feels further away than ever.

"If I arrive in Pamplona it will be a miracle of God," said Lopez, his voice filled with anguish.

- Epilogue -

But, as is rarely the case for Venezuelans these days, this story has a happy ending of sorts.

Two days after this interview on the road to Pamplona, Lopez contacted AFP to say he'd been picked up by an ambulance.