The “worms” that suck blood are commonly known as leeches and many have been used to treat ailments since ancient times. Early-day practitioners believed that medicinal leeches cured almost any ill. Today, they’re regaining a foothold with physicians and other medical experts for very specific treatments, including the healing of severed body parts and reducing the dangers of blood clots.
Approximately 650 leech species exist and, of those, about 15 are used in medicine. Hirudo medicinalis is the European medical leech and is used in a multitude of procedures. While the thought of a worm stuffing its body with your blood might be a bit disturbing, leeches have unique mechanisms for doing more good than harm. As cousins to the earthworm, these little “suckers” are saving severed extremities, speeding healing after reconstructive surgery, and even preventing strokes.
The leech, a type of segmented worm, is a complex creature with suckers on both front and rear ends. Its multiple “brains” or nerve bundles lie at the center of the body. Leeches can reach lengths of eighteen inches, but Hirudo medicinalis generally grows to about four inches. The mouth, or anterior, end collects the blood by sawing into the skin with tiny teeth. The rear, or anterior, sucker latches on as an anchor.
Feeding time is about 20-30 minutes. The leech can draw in up to ten times its body weight in blood. Once it is full, the leech detaches and can take several months to digest its meal. In medical environments, leeches are used only once and then discarded. Some individuals say there is a small sensation of pain; in a few cases as strong as an insect bite. However, leech saliva carries a natural anesthetic that deadens the skin as it bites and most people feel nothing at all.
While the medicinal leech transmits many compounds in its saliva, it is the anticoagulant hirudin that provides the greatest benefit. When clotting is a danger, a leech – or several of them working as tag teams – will inject hirudin at specific feeding points. During this process, the leech can suck up pooling blood around a wound or surgical scar and keep healthy blood flowing through the vessels.
Medicinal leeches come from private facilities where some are fed a diet of pig’s blood as they grow. Then, they are allowed to return to a hungry state and cooled down to prolong life. Unfortunately, these environments cannot be made sterile and the worms do carry a bacterium known as Aeromonas hydrophila. In the leech’s body, this acts as a digestive enzyme and keeps the blood from putrefying. A small number of cases report individuals contracting the bacteria, which can raise the risk of infection at the wound site. Patients receive an antibiotic prior to treatment to prevent this transmission.
Research continues into the benefits of replicating hirudin. Collecting the anticoagulant from leeches would be tedious as each worm produces very small amounts, prohibiting mass distribution.
Bloodletting is no longer recommended for headaches and other such complaints. Indeed, leeches are no longer a resource for maintaining a balance of the “humors” as they were in the days of Hippocrates. Experts now accept, however, that these sucking worms can perform vital services when other medical treatments fail.