Leeches: Little bloody marvels

By Kathy Riley 29 June 2009
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The bane of bushwalkers, leeches are a microsurgical miracle.

“I think I’ve got something in my eye.” Dan Harley turned around to find his field assistant, wet and muddy from their long trek through the Dandenong Ranges in Victoria, standing on the track and blinking uncertainly. “I saw what looked like a tiny speck of dust on her lower eyelid, near her lashes,” he says. “I asked her to pull her eyelid down so I could brush it off without hurting her eye, and when she did, this black thing appeared, gradually rolled up and dropped like a beached whale onto my hand. It was a big, fat leech, which had been feeding on the inside of her eyelid.”

Dan was fascinated and impressed – but then, he’s an ecologist. His assistant, on the other hand, was understandably horrified. It would have been little consolation to know that, given their location in Victoria, they were in the company of Richardsonianus australis – the medical celebrity of Australia’s 40 described leech species.

It’s been a long and rocky road to glory. Over the past 3000 years, leeches have been alternately hailed as miracle cure-alls and dismissed as medical quackery. Insomnia, gout, headaches, cancer and even obesity were all treated with leeches by well-meaning doctors who believed that such ailments resided in the patient’s “bad blood”. While medicine has clearly healed itself of that particular belief, leeches have been steadily working their way back into doctors’ medical kits. Today, an international army of medicinal bloodsuckers, the Australian contingent of which is R. australis, is increasingly being called upon to assist with advanced microsurgery, including the reattachment of fingers, toes and other misplaced appendages, skin grafts and plastic surgery.

“Microsurgery involves the suturing of arteries and veins to re-establish blood flow to a tissue or organ,” says Dr Nicholas Lotz, a spokesperson for the Australian Society of Plastic Surgeons. “The walls of arteries, which carry blood into an area, are much thicker than those of veins, which carry blood away. If, after surgery, the vein doesn’t recover well enough to re-establish a healthy circulation, blood builds up and the area becomes congested. This puts the patient at risk of losing that finger or nose or whatever.”

It’s in such emergency situations that the leech is summoned. “Patients are pretty grossed out at first,” says Katie Laing, a clinical nurse at Liverpool Hospital, NSW. “But leech therapy is the last resort. If you explain it that way – ‘Mr Smith, I’m sorry, but unless we try the leeches we’re going to have to take you back to theatre and you might lose that tip on the end of your nose’ – they usually say ‘okay, just do it’. And most of the time, by the end of the therapy they’re really into it.”

Katie is one of the leech’s biggest fans – which is lucky, because around 3000 of the suckers annually pass through the small fish tank she keeps in the hospital’s orthopaedics and trauma ward. “I come in here and talk to them,” she says. “When I see there’s a baby, I feel like a grandmother. I get very excited. But I have to stay a little bit remote, because they’re bred to be worked.”

It’s a hard life for the medicinal leech. To be effective they must be hungry, and as one feed can sustain a leech for up to 12 months, they’re kept well away from food until they’re needed. Once they’re finally allowed to sate their hunger on a patient, they’re dunked in salty water for five minutes, which forces them to vomit up their meal. After a 24-hour rest in the patient’s bedside drawer, it’s straight back to work. As it’s not yet certain whether leeches transmit blood-borne diseases, when their patient no longer needs them they’re dunked one last, fatal time – in a container of methylated spirits.

It’s a short life, but an incredibly useful one. “Leeches function in two ways,” explains Katie. “Primarily, they draw blood out, which relieves the congestion and pressure, but while they’re feeding, they’re putting in vasodilators, anticoagulants, anti-inflammatories and anaesthetic. Vasodilators make the blood vessels bigger, which helps the blood flow; anticoagulants stop the blood from clotting; and anti-inflammatories stop the big tissue proteins and white blood cells – which your body sends to heal the traumatised area – from arriving and blocking off the little veins.” Scientists couldn’t have mixed a more useful medicinal cocktail if they tried.

As the number of ailments for which leeches can be used grows (varicose veins, blood-clotting disorders and the reduction of swelling associated with arthritis are a few of the more recent additions) leech breeding has become a multimillion-dollar industry overseas, with companies in Europe and Russia pouring money into the extraction of medicinal compounds from leech saliva and the development of creams and cosmetics.

Australia’s leech industry, in comparison, is a backyard business. Brian and Carol Woodbridge began farming R. australis in Echuca, Victoria, 15 years ago, and now supply up to 5000 leeches a year to hospitals in WA, SA, Victoria and NSW – including Katie Laing’s stash in Liverpool Hospital. Brian says the demand is growing as word spreads. “If a doctor or a hospital doesn’t use leeches, it’s generally ignorance rather than dislike,” he says. “As doctors rotate around hospitals, they introduce others to leech therapy. I find if I make one sale to a new hospital I’ll generally make more.”

Brian and Carol’s farm consists of a 30sq. m dam, a couple of 20sq. m ponds, two 3m diameter ‘holding tanks’, and nine fish tanks (for breeding) in a temperature-controlled shipping container. Brian reckons they’ve currently got a few thousand leeches, but as he drily points out, “it’s a bit hard to do a stocktake”.

Fifteen years of observation has made Brian Australia’s leading medicinal-leech expert, but he’s still fine-tuning his farming techniques. His reluctance to share his trade secrets suggests he’s aware he’s sitting on a largely untapped vein of potential. “I’ve supplied to European doctors here who’ve told me this species is the best they’ve come across, based on the time they suck,” he says. “I don’t know about the science behind these things, but I reckon there’s a bright future for these guys.”

Try telling that to Australia’s bushwalkers. Decades of bloody socks and squeamishness have given rise to a battery of leech-repellent concoctions as diverse as salt, garlic, lemon juice, soap-suds and even tobacco mixed with cheap port. But according to Dan Harley, leeches have made suckers of us all. The easiest way to deal with them, he says, is to ignore them. “They don’t hurt,” he says. “They don’t leave any scars. They’ll take a bit of blood and then leave you alone. Where’s the harm in that?”

Source: Australian Geographic Jul- Sep 2007