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By Carol Rados
For thousands of years, leeches have been worming their way in and out of medicine as a questionable cure for anything from headaches to gangrene, reaching their height of medicinal use in the mid-1800s. Today, the slimy aquatic creatures are making a comeback as a legitimate treatment that can help heal skin grafts and restore blood circulation. Their primary function is to drain blood. Pooled blood around a wound can threaten tissue survival.
In June 2004, the Food and Drug Administration cleared the first application for leeches (Hirudo medicinalis) to be used in modern medicine as medical devices. By definition, a medical device is an article intended to diagnose, cure, treat, prevent, or mitigate a disease or condition, or to affect a function or structure of the body, that does not achieve its primary effect through a chemical action and is not metabolized.
Surgeons who do plastic and reconstructive surgery find leeches especially valuable when regrafting amputated appendages, such as fingers or toes. Severed blood vessels in such cases often are so damaged that they lack the ability to clear the area of blood. In these cases, it is difficult for the surgeon to make a route for blood to leave the affected part and return to circulation.
"The idea behind the leeches is to cause blood to ooze so that the body's own blood supply will eventually take over and the limb can go on and survive," says Rod J. Rohrich, M.D., president of the American Society of Plastic Surgeons and chairman of the Department of Plastic Surgery at the University of Texas Southwestern Medical Center. Leeches apply the perfect amount of suction to get the blood flowing. But Rohrich also says he uses the leeches only when there's a compromised situation, such as following surgery, "when the patient's own blood supply isn't adequate."
Packing a one-two chemical punch, the benefit of leech therapy comes not from the amount of blood that is extracted, but in the powerful anti-clotting agent hirudin, contained in the parasite's saliva, which keeps blood flowing freely. At the same time, leeches emit a natural anesthetic that minimizes pain during their feast.
Having disk-shaped suckers on each end of their bodies helps leeches feed, as well as hang on. The number of leeches used varies with each patient--typically two or three leeches are applied to the body until they drop off after about 40 minutes, and then the process is repeated with a new leech "team." At $7 to $10 apiece, their expense won't break budgets of physicians or hospitals.
The FDA considered safety data as part of reviewing the marketing application for the leeches submitted by Ricarimpex SAS of Eysines, France. In addition, the agency studied published literature on the use of leeches in medicine, how the leeches are fed, their environment, and the personnel who handle them.
Leeches were already being used in hospitals. A 1976 law has allowed companies that raised and sold medical leeches before that year to continue doing so. Newcomers seeking to market leeches for medical purposes, however, were required by the 1976 law to gain FDA approval.
You won't find the type of leeches approved for medical use in a lake, river, or swamp. Rudy Rosenberg, owner and vice president of Leeches USA Ltd., the initial importer and distributor for Ricarimpex in the United States, says the leeches are raised under optimum conditions in controlled basins and laboratories. The facilities are certified, and all lots are tracked. This, he says, protects patients from infection. Leeches drop off after "feeding," and must be treated as infectious waste material. Rosenberg says that he knows of no case of leech-borne infection having been reported.
How do people react to being treated with these slimy parasites? "Initially, they're repulsed by the idea of leeches as a treatment," says Rohrich, "but eventually, they come to terms with the fact that it may be saving their lives."