Leeches: Little bloody marvels

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