The largely unexplored Essequibo river snakes through Guyana's vast rainforest for more than 1,000km – and after kayaking its length, Pip Stewart felt fitter than ever.
The 34-year-old was part of the first team to paddle the entirety of South America's third longest river, from the source in the Acarai mountains, through untouched jungle to the river mouth at the Atlantic Ocean.
But three months after completing her "magical" journey, Stewart found herself hooked up to an IV in a hospital room in London, feeling weak and achy as her body was pumped full of toxic drugs.
The adventurer was battling a flesh-eating parasite – which was slowly consuming her neck.
"It looked like I had a gunshot wound," Stewart told The Telegraph. "It was just disgusting."
Despite donning full-length jungle gear throughout her trip, Stewart was covered in bites when she left Guyana, and most of them slowly disappeared, the Daily Telegraph reports.
But one sandfly bite was growing above her collar on the left of her neck, so she went to the London Hospital of Tropical Diseases to check out this "weird bite that wasn't going away".
A couple of weeks and a biopsy later, the adventurer was diagnosed with cutaneous leishmaniasis, an illness which causes skin lesions and ulcers, leaving behind life-long scars and, in extreme cases, disability.
It is the most common form of one of the world's most devastating parasitic diseases.
Each year, roughly one million people are infected with leishmaniasis, which is endemic in 98 countries – predominantly in Latin America and Africa. The most deadly form of the disease, visceral leishmaniasis, is fatal without treatment and kills between 26,000 and 65,000 people annually.
The vast majority of those affected live in remote corners of the globe with little or no access to health facilities, said Dr Byron Arana, head of cutaneous leishmaniasis at Drugs for Neglected Diseases initiative, the drug research and development not-for-profit.
"Leishmaniasis is a poverty-related neglected disease that affects neglected people mainly in developing countries," he told The Telegraph. "In complex cases, the disease can eat away at the face, eyes, ears and vocal cords. These cases are very difficult to treat."
Tackling the illness is costly and often involves painful injections of toxic drugs over many weeks. For most people in remote communities, access to such treatment is near impossible.
After Stewart's diagnosis, she contacted friends from Guyana to find out how their communities dealt with the flesh-eating parasite.
Options they recommended included searing the parasite out of the skin using burning cow fat, or treating the lesions with crushed turtle shells.
At the London Hospital of Tropical Diseases, the drugs Stewart was offered were hardly more appealing.
The adventurer was injected with toxic antimonials which – despite the high risk of pancreatic, liver and arthritic problems down the line – have been used to treat leishmaniasis for more than 50 years.
"Every day for three weeks I was going into hospital, spending about an hour and a half on an IV, being pumped full of this highly toxic drug," Stewart said. "Because it's a form of chemical therapy, my liver functions and my heart were monitored."
The treatment, she added, was more painful than the scabby pus-filled lesion growing on her neck.
"I constantly had to remind myself, as I was 21 days with an IV attached to my arm, that I was lucky, that I was having the best treatment available. But all the time I was questioning why there isn't a better option out there," Stewart said.
Efforts to develop alternative drugs have struggled, in part due to a lack of funding.
While there has been a new treatment for the deadly visceral leishmaniasis in the last decade – which, when administered in a single dose, has cured roughly 90 per cent of cases in India – there's been less success in tackling other forms of the parasitic illness.
"For cutaneous leishmaniasis, there is no such drug and that is why we continue using antimonials," said Dr Arana. "There is an urgent need to develop new, effective, affordable, oral, short-course treatments for leishmaniasis that are easy to administer."
After her experience last August, Stewart agrees, and is using her profile to raise awareness of the little-known but common disease – most recently delivering a TED Talk earlier this year.
"Getting leishmaniasis was probably the most physically exhausting thing I've ever had – the treatment, not the actual bite – and emotionally one of the hardest things I've ever been through," she said.
"One billion people are at risk [of leishmaniasis] in 98 countries. This is not a small scale thing, it has real global implications that we're just ignoring."