Knee-deep in murky water, with nothing but his trusty dungarees and a net, Brian Woodbridge is searching for something special.
He's not a treasure hunter — at least, not in the traditional sense. As far as he knows, Brian is Australia's only leech farmer.
"They'll lay on the bottom ... and if they sense any movement, they'll attack it," he says, dragging his net through the water.
You won't find Brian's stock on the supermarket shelves anytime soon, but he's part of a blood-thirsty practice that's been helping us heal for millennia.
Near the farming town of Echuca, on the border of Victoria and New South Wales, Brian breeds leeches for medical use.
These days, the parasites are used to help with things like reconstructive surgery and microsurgery, where they work to restore blood flow and prevent blood clots.
But they were once used like aspirin — and were even thought to be a treatment for obesity.
In fact, leeches were so widely used in medicine that at one point, Australia was exporting them to other countries where they were being driven to extinction.
Leeching starts with our quest to 'rebalance' the body
Take a walk down the halls of the University of Queensland's Mayne Medical School, and you'll find a seemingly ordinary ceramic jar tucked away in a glass display.
"This lovely leech jar here is an example of something that might have been in a chemist or pharmacy," says Charla Strelan, curator of UQ Medicine’s Marks-Hirschfeld Museum.
"It's missing the lid, but it would have been stocked up with rocks and moss, and it would have been quite moist, and the leeches would have been kept in that."
For thousands of years, bloodletting, or phlebotomy, has been a feature of medicine and the quest for health, with the practice once thought to help everything from seizures to headaches.
It might sound a bit strange in this day and age, but much of the idea behind it comes from a theory called the four humours, often credited to the Greek physician, Hippocrates.
According to this theory, an imbalance in the four bodily fluids — blood, yellow bile, black bile, and phlegm — could lead to different illnesses, and were connected to seasons, body parts and stages of life.
"This was kind of at a time in medical history where they hadn't yet really got into autopsies and looking inside, so they're looking at outward manifestations — people know about the black and yellow stuff that comes out of you and blood," Ms Strelan says.
"It was believed that these four things going through our bodies corresponded to the order of the universe, and that in order to be healthy, we needed to have those four humors in balance.
"So things like bloodletting, but also inducing vomiting or diuretics, were all treatments to 'rebalance' the body."
Leeches were used 'like we use aspirin nowadays'
The earliest clearly documented record of leeches being used for remedial purpose dates back to 1500 BC Egypt, and you'll find the parasite dotted throughout history and culture over thousands of years.
But it wasn't until the 18th and 19th centuries that they really found their foothold in medicine.
As Alexander Maier, a parasitologist with Australian National University explains, towards the end of the 1700s, "a few people thought it was a really, really good idea to reinvigorate that interest" in bloodletting.
Irrevocably, leeches became a household name, with health professionals using them as a treatment for everything from cancer to mental health conditions.
In the 1800s, British physician Thomas Tanner even wrote that applying them to the anus could be used as a treatment for obesity.
"At that time, France had 30 million inhabitants, and they used more than 100 million leeches a year," Professor Maier says.
"Basically, they used leeches as we use aspirin nowadays."
While business was booming, the unprecedented demand saw numbers of the animal dwindle to the point where "they were almost extinct in parts of Europe", Ms Strelan says.
Bloodletting sparked a lucrative international trade across Europe and to the USA, and even the development of new devices like the "artificial leech".
"[Leeches] became really quite fancy... You'd pay top dollar in the finest French hotels to get leeches," Ms Strelan says.
The demand was so great that at one point Australia was exporting leeches to Europe.
"A lot of poor people actually found it a good industry because they would walk through swamps, just with their skirts up, and catch leeches and then bottle them up and sell them on."
'Very often the patients died because of the treatment'
What goes up, must come down, and by the late 1800s, public sentiment began to shift away from leeches.
"Some historians describe it as the age of vampirism, because they absolutely overdid it," Professor Maier says.
"Some patients got more than 100 leeches put on them. Very often they died because of the treatment."
The real turning point, however, came when our view of what causes disease changed, he says.
The introduction of things like germ theory and cellular pathology — the idea "that disease is caused by metabolic imbalances, not bodily fluid imbalances" — dawned a new era in medicine.
It didn't mean the use of leeches stopped entirely. The practice "was still in the background", Professor Maier notes, particularly in countries where providing access to conventional healthcare was challenging.
But for the most part, it sat on the shelf until around the 1920s, before making a formal comeback in the 1970s.
"In the 1920s, some doctors decided to put it to the scientific method and find evidence why the leeches actually were so popular apart from that underlying philosophy [the four humours]," Professor Maier says.
"And indeed, in certain conditions, the use of leeches is very beneficial."
Leech therapy can save fingers (and more)
The power of leeches is something surgeon Sarah Tolerton understands all too well. She's part of a team at Sydney Hospital using the parasite on patients after reconstructive surgery.
Leeches release a naturally occurring anaesthetic into the skin when they bite so you can't feel them, and their saliva has anticoagulant properties, which can help prevent blood clots and promote blood flow.
Dr Tolerton is meeting with a patient named Cole, who has undergone complex microsurgery to reattach badly damaged arteries and veins in his fingers after an accident using a drop-saw.
If blood flow isn't restored, it can cause swelling and will eventually cut off the blood supply entirely, causing the finger to die.
"If you can't re-establish outflow from the finger, then what will happen is swelling, and that's when we'd start thinking about leeches," Dr Tolerton says.
"In Cole, it actually happened to his ring finger and that's where we did the leech therapy."
Leeches are also effective in plastic surgery, where they relieve venous congestion which can cause tissue to die in compromised skin flaps, adds Professor Maier.
These flaps have "very small blood vessels" and can cause the blood to coagulate, meaning that it stops flowing "and the tissue around it doesn't get enough oxygen," he explains.
"The leeches are actually very fine-tuned in injecting the right amount of anticoagulants so that the blood flows without harming the tissue."
A strange but wonderful creature
From the Bronze Age to modernity, these blood-sucking parasites may not look like much, but they've played an important (and strange) role in medicine and our wider understanding of it.
So next time you find yourself out in nature, take a moment to reflect on "what a wonderful creature the leech is", Professor Maier quips.
"I get annoyed when I go walking and I get a leech on me, but think about all the biological opportunities and medical opportunities that this organism actually contains," he says.
Wading through a muddy creek bed in regional Victoria, it's not a sentiment lost on Brian Woodbridge.
"Australia's only leech farmer" may not be the most glamorous job title, but each and every parasite he scoops into his net will go on to play a unique and crucial role of their own.
Who knows, they might even help save your finger one day.
Parasites are all around us. Learn more about these complex little creatures and how scientists try to harness their power for good on the Catalyst episode Monsters Or Medicine? on ABC TV and ABC iview.
