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Leeches have been used in medical bloodletting practices for nearly 3,000 years. Using the Hirudo medicinalis species of leech and a handful of others, hirudotherapy practitioners attempt to cure patients of a range of conditions, from easing hypertension and improving circulation to easing the symptoms of herpes and removing blood clots. Though nowhere near as widespread as before the 20th century, hirudotherapy still is commonly taught to many reconstructive and plastic surgeons across the globe, who use these leeches for their anesthetic and anticoagulant secretions.
The hirudotherapy leech that is used for medical purposes in 2011 should be obtained from sterile laboratories — a requirement of many countries that allow the use of these treatments. This obviates worries about inadvertent infections. Before the middle of the 20th century, however, hirudotherapists may have collected their leeches from a nearby pond or ditch.
Before 1950, dating back to Egypt and India of 1000 B.C., leeches were commonly used in several cultures for the process of bloodletting, called venesection. According to Gilbert Seigworth, a physician in Vestal, New York, the process entailed draining a vein at key locations around the body with the simple painless bite of a leech. The anticoagulants then keep the blood flowing from the body until the leech is about three times is normal size. These techniques were used to lessen blood pressure by reducing volume, ease menstrual cramping, reduce fevers, and prevent a range of infectious diseases.
Of the approximately 650 species of leeches, most have bites that are painless, due to the anesthetic nature of their mouth secretions. A few, however, exhibit the anti-clotting supremacy of Hirudo medicinalis. Even in 2011, some surgeons praise medical leeches as important tools in surgical procedures during which the blood's natural clotting mechanism must be suspended.
Many nonsurgical practitioners of hirudotherapy go about their treatments in a way that can be compared to acupuncturists. The latter treatment involves painlessly inserting needles at the body's various nerve centers and reflex points, with the pattern depending on the overall desired effect. Hirudotherapy often follows the same principles, particularly when applied for preventative health.
Most modern medical treatments have evolved beyond hirudotherapy, employing medicinal compounds far more complex than what is secreted by Hirudo medicinalis. This lowly creature of the dirt, however, is credited with helping to point researchers and physicians in the right direction. The leech, though it contains dozens of "brains," has a circulatory system that closely mirrors the human body. Scientists have used the animal to test new drugs planned for human use.
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