You'll find the original transcript of this Insight episode on SBS's site here. I've enhanced it a little by adding some still shots, which I digitally grabbed by feeding a video of the show into the back of my computer. (It's the next best thing to an mpeg.)

EACH YEAR AT LEAST THREE MILLION AUSTRALIANS HEAD OFF OVERSEAS...ON BUSINESS, ON HOLIDAYS, OR TO VISIT FRIENDS AND RELATIVES. ALMOST ONE IN THREE OF THESE TRAVELLERS FLY TO EXOTIC AND DANGEROUS DESTINATIONS... THE BACKBLOCKS OF ASIA, THE JUNGLES OF AFRICA.

Traveller: "Have you got your passport? Where are you flying to? Harare? Okay, have you got your passport and ticket there please. Yes I do"

BUT WHAT MANY DON'T REALISE IS THAT ONE THE BIGGEST DANGERS THEY COULD FACE IS FROM SOMETHING THEY'RE CARRYING WITH THEM. A DRUG, DESIGNED FOR THEIR PROTECTION, THAT'S DRIVING SOME PEOPLE INTO DEEP DEPRESSION, HALLUCINATIONS, THOUGHTS OF SUICIDE, EVEN SELF-MUTILATION...

ALMOST FIVE YEARS AGO, SHELDON JOHNSTON WAS ONE OF THOSE AUSTRALIANS OFF TO SEE THE WORLD. A FIT, ADVENTUROUS YOUNG MAN AND A SEASONED TRAVELLER, HE WAS ABOUT TO EMBARK ON A SEVEN MONTH ADVENTURE IN AFRICA...

Sheldon Johnston: "I was on an overland truck trip going through Africa., I started in London..."

BEFORE HE LEFT LONDON, SHELDON WAS CAREFUL TO GET ALL THE ROUTINE MEDICAL PROTECTION HE NEEDED, INCLUDING ANTI-MALARIALS...

Sheldon Johnston:"I didn't really even see a doctor, I just saw a practice nurse whose job it was to jab me with a needle and send me on my way with a prescription."

THAT PRESCRIPTION WAS ABOUT TO TAKE SHELDON JOHNSTON ON A JOURNEY INTO HELL....

Sheldon Johnston: "I thought my body was just adjusting and I'd gotten through it after a week, but one little illness after another, what I mistakenly thought was a cold, dehydration sickness, what was misdiagnosed as malaria and typhoid, all along the way I visited five hospitals in Nigeria and Cameroon."

EVENTUALLY, SHELDON SUFFERED A SEIZURE IN THE WILDS OF CAMEROON, AND FINISHED UP, EMACIATED AND EXHAUSTED, IN YET ANOTHER TINY HOSPITAL...

Sheldon Johnston: "So I was on a drip overnight in this small village hospital, and I would say that I was gravely ill at that stage. I think a few of my travel companions in hindsight were actually afraid that I was going to die..."

WE MOVE FORWARD A YEAR NOW, TO 1996. ANOTHER YOUNG AUSTRALIAN ON ANOTHER DREAM HOLIDAY IN AFRICA....

Lesley Gidding: "I just wanted to backpack around East Africa, and so I landed in Zimbabwe and worked my way up to, through Malawi, Tanzania, Kenya and Uganda, and I worked in Tanzania and then headed off to Kenya and Uganda"

LESLEY GIDDING ALSO GOT ALL HER VACCINATIONS AND HER ANTI-MALARIALS. AND, LIKE SHELDON, HER TRIP WAS ABOUT TO TURN INTO A NIGHTMARE...

Lesley Gidding: "I remember, actually I was reading my journal last night to remind me of how I was feeling at that time, and I was writing that my head was spinning, and that I was in this haze, and I didn't quite under stand where I was or what was happening to me and I was really scared"

Lesley reading: "16^th March 1997. I'm tired, numb and hazy headed. I'll probably maybe if I can write again when things become clearer."

"I don't feel anything. Nothing. Absolutely nothing feels real to me at the moment, and hasn't done for a long long time."

A VIDEO SHOT BY LESLEY'S FRIENDS AT THE TIME SHOW HER PUTTING A BRAVE FACE ON HER AFRICAN HOLIDAY, BUT BEHIND THE SCENES THINGS WERE VERY DIFFERENT...

LESLEY HAD BOUTS OF FEVER, FLU-LIKE SYMPTOMS AND VOMITING. BUT THAT WAS NOTHING COMPARED TO WHAT HER MIND WAS GOING THROUGH...

Lesley Gidding: "I went into this really weird, I won't call it a depression, but it was more like anxiety and paranoia. I really thought that people were following me, I really thought that people were going to hurt me."

MONTHS EARLIER, IN A DIFFERENT PART OF AFRICA, SHELDON JOHNSTON HAD BEEN EXPERIENCING THE SAME MENTAL SYMPTOMS ALONG WITH HIS PHYSICAL SUFFERING...

Sheldon Johnston: "It was like there was a fog over my brain, and wading through glug just trying to keep my eyes open."

"I was also very depressed for no reason, but, to the point where I realised it was madness, there was just no reason behind it, I would almost sort of, errrr, shake my head and think, no I'm not really that sad about being here on holiday and having a good time, you know."

EVENTUALLY, SHELDON BECAME SO SICK HE WAS FLOWN TO LONDON. AT THE HOSPITAL FOR TROPICAL DISEASES IN KINGS CROSS, THE CAUSE OF HIS ILLNESS WAS FINALLY DISCOVERED...

Sheldon Johnston: "After waiting, I was seen by a doctor, after about fifteen minutes of consultation, he was very quick to deduce that I'd probably had mefloquine toxicity."

MEFLOQUINE... MARKETED AROUND THE WORLD UNDER THE BRAND NAME LARIAM. IT'S A HIGHLY EFFECTIVE PREVENTION AND TREATMENT FOR MALARIA. BUT THERE'S A CATCH.

WHEN SHELDON ARRIVED BACK IN SYDNEY, AN EMACIATED AND SICK MAN, HE'D DISCOVERED FROM BITTER EXPERIENCE THAT LARIAM CAN CAUSE SEVERE NEURO-PSYCHIATRIC SIDE EFFECTS IN SOME USERS....