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LEECHES: New Uses for an Old Remedy

Why are leeches called bloodsuckers? Do they really suck blood? Yes, they do, and their role as bloodsuckers could help save your life.

For centuries, leeches were used in medical practice. In the second century C.E., the Greek physician Galen described the use of leeches in removing blood from patients in a procedure called bloodletting. An excess of blood in the body was believed to be responsible for a variety of illnesses, from headaches and fevers to heart disease. Physicians used the leeches to remove this "bad blood" from a patient's body.

Bloodletting was common in Europe through the early 1800s. During the late 19th century, however, medical science discredited the idea that excess blood causes disease, and bloodletting fell out of favor.

Uses in Microsurgery

Leeches are making a comeback in medicine, although with new purposes. One of these purposes is to increase the success rate of surgical operations to reattach severed limbs, fingers, ears, or toes. Such operations involve microsurgery, a process in which surgeons reconnect tendons, blood vessels, and nerves by using tiny instruments and powerful microscopes. However, in some microsurgery, physicians cannot reconnect tiny, delicate blood vessels. As a result, circulation in the reattached limb, finger, or toe is impaired.

The tissues may become congested with blood. If congestion occurs, the tissues of the reattached part will not heal and will eventually die.

One solution to this congestion problem is to place leeches on the reattached body part. Once attached to the wound site, the leeches begin to suck out the accumulated blood, relieving congestion and allowing the tissues to remain healthy until the veins can grow back. At about $10 each, leeches are a relatively inexpensive treatment for a serious problem.

Uses as Anticoagulants

Leeches have medical uses that go beyond their ability to remove blood. Scientists have known since the 1800s that leech saliva contains a powerful anticoagulant, a substance that inhibits blood clotting. The leech's anticoagulant, called hirudin, can cause four hours or more of steady bleeding.

Leeches have been applied to this patient's sutures across his upper back to reduce blood congestion. Each leech can remove up to 5 mL of blood.

The steady bleeding helps prevent blood from clotting so the leech can feed freely.

New Applications

Today, hirudin is made through genetic engineering, without the aid of leeches. It has proven useful in the treatment of some heart patients, particularly those who have had heart attacks, who suffer from angina, or who have undergone angio-plasty, a procedure to open blocked arteries. One research study even indicated that hirudin may be effective against the spread of cancer.

The amazing uses that have been found for a substance in leech saliva are encouraging to medical researchers, who continue to explore how knowledge of invertebrate organisms can be beneficially combined with medical technology.

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