THE cardboard box marked “Emergency Medical Shipment” thumps down on Lillian Jackson’s desk in the supplies department at Vanderbilt University Medical Center in Nashville, Tennessee. Inside she finds a sealed plastic bag of water in which dozens of small black creatures are happily swimming around. Leeches, again! Without hesitation, Jackson sends the creatures to the hospital’s trauma unit, where nurse Rene Kopp takes charge. Over the next few days, Kopp will apply the leeches to chosen patients – to suck their blood. “We’ve been doing it for years,” says Jackson.
Leeches have indeed been used in medicine for years – for millennia, in fact. They were once believed to remove illness-causing fluids, or “humours”, from the blood. In reality they probably had little effect, and by the late 19th century such bloodletting had fallen out of favour. In the early 20th century, however, it occurred to surgeons that the slimy annelids might have a useful medical role after all. Leech bloodlust, they figured, was just the thing to help treat a dangerous complication after surgery to reattach torn or severed body parts such as fingers, ears or flaps of skin. Excess blood can collect in the reattached part, which, if left untreated, can cause tissue death and even be life-threatening.
Leeches are perfect for relieving “venous congestion”, as this phenomenon is known. “The leech’s primary role is to act as a vein,” explains Richard Miller, medical director of the Vanderbilt trauma unit. In addition to the blood it consumes, the leech injects chemicals that stop blood clotting, which keeps blood flowing from the wound after the beast leaves.
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The medical leech, Hirudo medicinalis, was approved by the US Food and Drug Administration (FDA) for post-surgical care in 2004 but it’s fair to say doctors have not yet completely got to grips with these living medical devices. Leeches can be unpredictable. They may go on strike at the bedside, refusing to latch on where they are needed. Or in the middle of feeding, they may lose interest and creep away. “They do fall into the sheets,” Miller admits.
Sheep-gut condoms
Perhaps their erratic behaviour is understandable, as they travel an awfully long way to lend a hand – or rather a sucker. The leeches that Jackson rushes to the trauma unit start life in the French coastal village of Audenge, close to the city of Bordeaux. Ricarimpex, the company that breeds them, has been in the business since 1845, when leeches were still thought to work by removing bad humours. The firm sells over 250,000 leeches a year to hospitals around the world and is the only FDA-approved supplier.
At the Ricarimpex nurseries, leeches enjoy a pampered existence in artificial ponds designed to mimic the ideal natural habitat. The water is kept at neutral pH and is free of pollutants and predators.
From birth to adulthood, the growing leeches get the royal treatment. Twice a month, Ricarimpex’s handlers don rubber waders and gently scoop up newborns from the basins. The leech babies are taken to laboratories where for the next 18 months they dine on chicken blood served in sheep-gut condoms. Once they reach adult size, at about 10 centimetres long, 5000 leeches will be loaded together in damp cotton bags, delivered to pressurised Air France cargo holds, and flown to destinations around the globe.
Leeches headed to the US may have a stopover on Long Island, New York, where they are held in aquariums at Leeches USA, one of the largest US distributors. Here, they pass into the care of Rudy Rosenberg, the company’s vice-president. “The leeches are beautiful and graceful,” he says, admitting that he sometimes gives them names.
When an order comes in, however, the time for such sentimentality is over, and the creatures are out of the door in moments to be flown to customers around the US. When a patient develops venous congestion, time is of the essence, so the company keeps a contingent of leeches on standby at New York’s JFK airport for after-hours emergencies.
Back in Vanderbilt Medical Center, Kopp places her newly arrived charges in a container that looks something like a spaghetti strainer, which drains and collects leeches from their watery residence. The container, known as a leech mobile home, then goes in a fridge at the bedside of a patient with venous congestion.
“Attach one leech to area every 4 hours,” might be a typical prescription, and it will usually be accompanied by one for a course of antibiotics. Even leeches raised in tightly controlled conditions harbour Aeromonas hydrophila bacteria in their saliva, which could cause sepsis, a serious blood infection.
Armed with gloves and tweezers, Kopp picks out a leech and places it on the site where blood is collecting. If all goes well, the leech will latch on. Its minuscule teeth puncture the skin, then its circular mouth holds on tight while sucking up its bloody meal.
Despite a popular belief that leeches inject a numbing agent, no such substance has yet been isolated from the creatures’ saliva (). Mark Siddall, head of the Leech Lab at the American Museum of Natural History in New York City, is not surprised. He has plenty of personal experience by which to judge the issue: “I’ve been fed on by these guys enough and, I’ll tell you, it hurts.”
Despite having been starved for the last three months, there are no guarantees that a leech will latch on, or drink its fill. Perhaps, speculates Siddall, they are disoriented or frightened by being handled. “I like to eat pizza,” he muses, “but if a huge pizza several million times my size picked me up, I probably wouldn’t turn around and take a bite.”
“If a huge pizza several million times my size picked me up I probably wouldn’t turn around and take a bite”
The medical staff take care to account for each and every one of the creatures applied to their patients. In one recorded case, a leech crawled between the stitches of a breast reconstruction incision and lodged itself inside the patient’s chest (). “You’ve got to know how many go on and how many go off,” says Miller.
Surgeons and nurses have come up with several tricks to prevent leeches from straying. In a modern spin on medieval leech cups, some construct a makeshift “leech cage” by cutting a small hole in the bottom of a disposable plastic cup and covering the top with clear film wrap. More sophisticated strategies include trapping the leech in a syringe and focusing it on its fleshy target, using surgical glue, or even stitching the animal to the patient’s skin (). Siddall advocates the gentler approach of tying a lasso around the leech’s hind anchor sucker after it latches on.
Fifteen to 20 minutes later, the leech will have gorged itself and swollen to six or seven times its original size. The creature tumbles off the wound. It cannot be reused because of the risk of passing on blood-borne infections, and a brutal fate awaits.
Kopp reaches for her tweezers and drops the leech into a tub of alcohol. Within minutes it is dead. Kopp tosses the shrivelled body into a red bag marked “Medical Waste” and removes her gloves. The leech’s long journey is over.
