Leeches


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Related to Leeches: Medicinal leeches

Leeches

 

Definition

Leeches are bloodsucking worms with segmented bodies. They belong to the same large classification of worms as earthworms and certain oceanic worms.
Leeches can primarily be found in freshwater lakes, ponds, or rivers. They range in size from 0.2 in (5 mm) to nearly 18 in (45 cm) and have two characteristic suckers located at either end of their bodies. Leeches consume the blood of a wide variety of animal hosts, ranging from fish to humans. To feed, a leech first attaches itself to the host using the suckers. One of these suckers surrounds the leech's mouth, which contains three sets of jaws that bite into the host's flesh, making a Y-shaped incision. As the leech begins to feed, its saliva releases chemicals that dilate blood vessels, thin the blood, and deaden the pain of the bite. Because of the saliva's effects, a person bitten by a leech may not even be aware of it until afterwards, when he or she sees the incision and the trickle of blood that is difficult to stop.
For centuries, leeches were a common tool of doctors, who believed that many diseases were the result of "imbalances" in the body that could be stabilized by releasing blood. For example, leeches were sometimes attached to veins in the temples to treat headaches. Advances in medical knowledge led doctors to abandon bloodletting and the use of leeches in the mid-nineteenth century. In recent years, however, doctors have found a new purpose for leeches—helping to restore blood circulation to grafted or severely injured tissue.

Purpose

There are many occasions in medicine, mostly in surgery and trauma care, when blood accumulates and causes trouble. Leeches can be used to reduce the swelling of any tissue that is holding too much blood. This problem is most likely to occur in two situations:
  • Trauma. Large blood clots resulting from trauma can threaten tissue survival by their size and pressure. Blood clots can also obstruct the patient's airway.
  • Surgical procedures involving reattachment of severed body parts or tissue reconstruction following burns. In these situations it is difficult for the surgeon to make a route for blood to leave the affected part and return to the circulation. The hardest part of reattaching severed extremities like fingers, toes and ears is to reconnect the tiny veins. If the veins are not reconnected, blood will accumulate in the injured area. A similar situation occurs when plastic surgeons move large flaps of skin to replace skin lost to burns, trauma or radical surgery. The skin flaps often drain blood poorly, get congested, and begin to die. Leeches have come to the rescue in both situations.

Precautions

It is important to use only leeches that have been raised in the laboratory under sterile conditions in order to protect patients from infection. Therapeutic leeches belong to one of two species—Hirudo michaelseni or Hirudo medicinalis.

Description

One or more leeches are applied to the swollen area, depending on the size of the graft or injury, and left on for several hours. The benefits of the treatment lie not in the amount of blood that the leeches ingest, but in the anti-bloodclotting (anticoagulant) enzymes in the saliva that allow blood to flow from the bite for up to six hours after the animal is detached, effectively draining away blood that could otherwise accumulate and cause tissue death. Leech saliva has been described as a better anticoagulant than many currently available to treat strokes and heart attacks. Active investigation of the chemicals in leech saliva is currently under way, and one anticoagulant drug, hirudin, is derived from the tissues of Hirudo medicinalis.

Aftercare

The leeches are removed by pulling them off or by loosening their grip with cocaine, heat, or acid. The used leeches are then killed by placing them in an alcohol solution and disposed of as a biohazard. Proper care of the patient's sore is important, as is monitoring the rate at which it bleeds after the leech is removed. Any clots that form at the wound site during treatment should be removed to ensure effective blood flow.

Risks

Infection is a constant possibility until the sore heals. It is also necessary to monitor the amount of blood that the leeches have removed from the patient, since a drop in red blood cell counts could occur in rare cases of prolonged bleeding.

Key terms

Anemia — A blood disorder marked by low hemoglobin levels in red blood cells, which leads to a deficiency of oxygen in the blood.
Anticoagulant — A chemical or medication that prevents blood from clotting.

Resources

Periodicals

Daane, S., et al. "Clinical Use of Leeches in Reconstructive Surgery." American Journal of Orthopedics 26, no. 8 (August 1997): 528-532.
References in periodicals archive ?
Leeches as further potential vectors for rickettsial infections.
Thousands of years since leeches were first employed for medicinal purposes, and a century since "leech mania" saw blood-letting used to tackle everything from headaches to strangulation, these creatures are still used to clean wounds and improve circulation, especially after surgery.
The import had dropped to 2,000 leeches per year by 1940 at 20% of the previous price.
Tan knows the explorers and has let one of their lab leeches stroll on her skin (it did not bite).
Leeches are hermaphrodites, meaning they have male and female reproductive organs.
He asked a scientist who was looking for saola in Vietnam to pick some leeches off the ground.
From spring through summer, leeches require substrates they can adhere to, avoiding bottoms of pure clay or mud.
Leeches are hermaphrodites, varying in shape, color and length.
Leeches are generally used during the critical postoperative period when venous outflow cannot match the arterial inflow, which can lead to venous congestion, clinically identified by the dusky purple appearance of the skin.
Leeches are annelids comprising the subclass Hirudinea.
The saliva of leeches contains many bioactive substances, which can prove helpful for patients.