Leeches have been used in medicine for thousands of years. Leeches remove blood ("phlebotomize") from their host, and they release pain-killing (anesthetic) and blood-thining (anticoaggulant) substances with their saliva. Live leeches are currently used to treat blood-congested limbs, which otherwise might die or require amputation, if the pooling blood cannot be removed any other way. They are also sometimes used to provide pain relief, and for many other therapeutic effects.
History of Leech Therapy
Leech therapy has a long history. Records indicate that Egyptians used leech therapy 3,500 years ago. Leech treatments were very popular during the Middle Ages. Again leech therapy became was commonly practiced in the 1800's by American physicians treating a variety of diseases.
In the 1980, medicinal leech therapy got a big boost by plastic surgeons who used leeches to relieve venous congenstion, especially in transplant surgery. This use of leech therapy ("hirudotherapy") provides a good example of its current status. When appendages are re-attached following traumatic amputation, it is often possible to reconnect the largfer arterial blood vessels, but not the thinner, more delicate venous vessels. The body will eventually develop the necessary venous connections to drain the area of oxygen-depleted blood; but if this does not occur rapidly enough, the pooling venous blood can produce enough swelling and pressure that fresh arterial blood may no longer be able to enter the re-connected limb. In this situation, leeches are used to drain the local blood and decompress the pressure within the grafted limb, otherwise at risk of necrosis (death).
Today, Medicinal leeches are also used in the treatment of other veinous deseases such as thrombophlebitis, as well as angina pectoris, arthritis, hematomas, and even tinnitus.
Natural History of Leeches
The medicinal leech (Hirudo medicinalis) is a segmented worm (Phylum: Annelida). This phylum includes the Polychaetes, the Oligochaetes (earthworms) and the Hirudinea (leeches).
Leeches have two "suckers," one at each end. The caudal (back end) suction cup helps the leech to ambulate on dry surfaces, and to attach to its host; the rostral (front end) suction cup also contains the mouth with three sharp jaws that leave a Y-shaped bite.
The medicinal leech lives in clean waters. Leeches swim free in the water, with an undulating motion. When attached to its host for feeding, the leech remains in place for 30 minutes to 6 hours or more, as it fills with blood. During feeding, H. medicinalis can suck 5 - 15 mL of blood --- several times its own body weight.
Leech saliva contains several bioactive substances, including anti-cooaggulants, vaso-dilators, and anesthetics. Hirudin, a potent anticoagulant in leech saliva, inhibits the conversion of fibrinogen to fibrin, preventing blood from clotting. Indeed, a wound may continue to bleed for many hours after the leech has already detached.
The benefits of leech therapy are due, in large part, to the anti-coaggulant effects, vasodilatory effects, and anesthetic effects of these biochemicals, as well as the physical effects of blood letting (phlebotomy).
Like a snake, the leech periodically must shed its skin. The leech is hermaphtroditic, having both male and female elements. Fertilization and egg-laying usually occur during the spring, summer, and winter months. Young leeches feed on the blood of small water animals (frogs, toads or fish). Leeches may not be ready for medical application until they are several years old.
Clinical Practice of Leech Therapy
The application of leech therapy is simple: leeches are gently placed in the area needed, and allowed to attach and engorge for the next 6-12 hours, after which they will release. The entire course of treatment may require one to 6 treatments or more, depending upon the goals and rate of response.
For more details about the specific application procedures, readers are referred to the manufacturer's directions. A list of manufacturers can be found elsewhere on this site.
Leeches (Hirudo Medicinalis) have been used medically for more than 1500 years. Originally used to remove “bad blood,” the leech is now used extensively by reconstructive surgeons needing to remove stagnant blood from a flap or reattached limb. When the venous blood does not return to the heart, it pools in the wounded area, increasing pressure and preventing fresh arterial blood from entering the area with oxygen and nutrients. The venous blood must be removed and the pressure must be reduced in order to save the flap or limb. The leech is able to do this exceptionally well, because its saliva contains important biochemicals, including vasodilators, anticoagulants, and anesthetics.
The leech will withdraw approximately 5 ml (one teaspoon) of blood. Further therapeutic benefit of leech therapy comes after the leech is removed, during which up to 50 mls of blood will continue to ooze, for up to 48 hours. More leeches attached to the site mean more blood will be removed. After 3-7 days, the veins have usually reconnected themselves such that the blood is no longer pooling in the limb. Normal color and pressure should return to the area, as arterial blood circulates easily in the damaged zone. By that time, the wound will be able to heal, without further phlebotomy (leech therapy).
The application of leeches to the patient is relatively simple, but does require care. As few as one, or as many as 6 or more leeches may be required for a wound, depending upon its size and its clinical response. The greatest number of leeches should be applied to the area of maximal venous congestion.
The patient’s skin must be cleaned thoroughly with soap and water, and then rinsed with distilled, non-chlorinated water. A gauze barrier around the area intended for the leech will help prevent the leech from wandering away from the site where it’s attachment is desired. It can be carried to the site by hand, or it can be placed within a 5 cc plastic syringe (plunger removed) and then applied to the wound site, containing the leech until it is attached.
If the leech is reluctant to bite, it might be necessary to entice it with a tiny droplet of blood, drawn from the wound site with a needle prick.
Once the leech is attached, it will likely remain safely in place until fully distended. The gauze square can be removed and used elsewhere without disturbing the animal;however, it is important that the site be checked continuously to insure that the leech hasn't moved. The leech will let go of the patient (host) when it is finished (usually within an hour).
What's New in Leech Therapy
In June, 2004, the U.S. Food and Drug Administration cleared for medical leeches for marketting by Ricarimpex SAS, based in France.