European Medical Leech

Taxobox
name = European Medical Leech
status = LR/nt
status_system = IUCN2.3

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image_width = 220px
image_caption = European Medical Leech in the wild
regnum = Animalia
phylum = Annelida
classis = Clitellata
ordo = Hirudinea
familia = Hirudidae
genus = "Hirudo"
species = "H. medicinalis"
binomial = "Hirudo medicinalis"
binomial_authority = Linnaeus, 1758

Medicinal leeches are any of several species of leeches, but most commonly "Hirudo medicinalis", the European Medical Leech.

Other "Hirudo" species sometimes used as medicinal leeches include (but are not limited to) "Hirudo orientalis", "Hirudo troctina" and "Hirudo verbana". The Asian Medical Leech is "Hirudinaria manillensis", and the North American Medical Leech is "Macrobdella decora".

Morphology

General morphology follows that of most other leeches. Fully mature adults can be up to 20cm in length and are green, brown or greenish brown with a darker tone on the dorsal side and a lighter ventral side, the dorsal side also has a thin red stripe. These organisms have two suckers, one at each end, called the anterior and posterior sucker. The posterior is mainly used for leverage while the anterior sucker, consisting of the jaw and teeth, is where the feeding takes place. Medicinal leeches have three jaws (tripartite) that look like little saws, and on them are about 100 sharp teeth used to incise the host. The incision leaves a mark which is an inverted Y inside of a circle. After piercing the skin and injecting anti-coagulants (Hirudin) and anaesthetics they suck out blood. Large adults can consume up to 15 grams of blood in a single meal. Medicinal leeches are hermaphrodites which reproduce by sexual mating, laying eggs in clutches of up to 50 near (but not under) water, and in shaded, humid places.

Range and ecology

Their range extends over almost the whole of Europe and into Asia as far as Kazahkstan and Uzbekistan. Over-exploitation in the 19th Century has left only scattered populations and reduction in natural habitat though drainage has also contributed to their decline. Another factor has been the replacement of horses in farming (horses were medicinal leeches' preferred food source) and provision of artificial water supplies for cattle. As a result this species is now considered vulnerable by the IUCN and European Medicinal Leeches are legally protected through nearly all of their natural range. They are particularly sparsely distributed in France and Belgium, and in the UK there may be as few as 20 remaining isolated populations (all widely scattered), the largest (at Lydd) is estimated to contain several thousand individuals, 12 of these areas have been designated Sites of Special Scientific Interest. There are small transplanted populations in several countries outside their natural range including the USA.

The preferred habitat for this species is muddy freshwater pools and ditches with plentiful weed growth in temperate climates.

Medicinal use

In the past

In medieval and early modern medicine, the medicinal leech ("Hirudo medicinalis" and its congeners "Hirudo verbana", "Hirudo troctina" and "Hirudo orientalis") was used to remove blood from a patient as part of a process to "balance" the "humors" that, according to Hippocrates, must be kept in balance in order for the human body to function properly. (The four humors of ancient medical philosophy were blood, phlegm, black bile, and yellow bile.) Any sickness that caused the subject's skin to become red (e.g. fever and inflammation), so the theory went, must have arisen from too much blood in the body. Similarly, any person whose behavior was strident and "sanguine" was thought to be suffering from an excess of blood.

Hirudotherapy, the use of medicinal leech for medical purposes, was introduced by Avicenna in "The Canon of Medicine" (1020s). He considered the application of leech to be more useful than cupping in "letting off the blood from deeper parts of the body." He also introduced the use of leech as treatment for skin disease. Leech therapy became a popular method in medieval Europe, namely the leeches from Portugal and France, due to the influence of his "Canon". A more modern use for medicinal leech was introduced by Abd-el-latif al-Baghdadi in the 12th century, who wrote that leech could be used for cleaning the tissues after surgical operations. He did, however, understand that there is a risk over using leech, and advised patients that leech need to be cleaned before being used and that the dirt or dust "clinging to a leech should be wiped off" before application. He further writes that after the leech has sucked out the blood, salt should be "sprinkled on the affected part of the human body." [Nurdeen Deuraseh, "Ahadith of the Prophet (s.a.w) on Healing in Three Things (al-Shifa’ fi Thalatha): An Interpretational", "Journal of the International Society for the History of Islamic Medicine", 2004 (3): 14-20 [18] .]

In modern medicine

Medicinal leeches are now making a comeback. They provide an effective means to reduce blood coagulation, relieve venous pressure from pooling blood, especially after plastic surgery, and stimulate circulation in reattachment operations for organs with critical blood flow, such as eye lids, fingers, and ears.

Because of the minuscule amounts of hirudin present in leeches, it is impractical to harvest the substance for widespread medical use. Hirudin (and related substances) are synthesised using recombinant techniques.

They are also being used in relation to the treatment of various Varicose conditions.

http://www.medicalleech.info/varicose-veins.htm

Devices called "mechanical leeches" have been developed which dispense heparin and perform the same function as medicinal leeches, but they are not yet commercially available. [Salleh, Anna. [http://www.abc.net.au/science/news/health/HealthRepublish_439856.htm A mechanical medicinal leech?] "ABC Science Online." 2001-12-14. Retrieved on 2007-07-29.] [Crystal, Charlotte. [http://www.virginia.edu/topnews/releases2000/cottlerleech-dec-14-2000.html Biomedical Engineering Student Invents Mechanical Leech] "University of Virginia News". 2000-12-14. Retrieved on 2007-07-29.] [Fox, Maggie. [http://www.otoweb.org/news_folder/mech_leech/mech_leech_A.htm ENT Research Group Recognized for Mechanical Leech Project] "Otoweb". University of Wisconsin, Madison, Division of Otolaryngology. Retrieved on 2007-07-29.]

uggested correction to photograph

The picture above does not represent "Hirudo". Hirudo looks like this: Pictures of the two most common species of "Hirudo", "H. medicinalis" and "H. verbana" may be found at [http://www.nsf.gov/news/news_summ.jsp?org=DEB&cntn_id=108657&preview=false www.nsf.gov] and [Siddall, M. E., Trontelj, P., Utevsky, S. Y., Nkamany M., Nacdonald, K.S.: "Diverse molecular data demonstrate that commercially available medicinal leeches are not Hirudo medicinalis." Proc. Biol. Sci. 274:1617 (2007) 1481–7] .

References

* [http://www.Hirudolab.com Hirudolab, Clinical information including contra-indication, and worldwide supplier to hospitals and research laboratories.]
* [http://www.leechesturkey.com Medicinal Leech, Turkey, Supplier of Medicinal Leeches]
* [http://www.leeches.biz/safety-adverse-effects.htm Information about Safety and Adverse Effects of Leech Therapy]
* [http://www.disgustingly-healthy.com Documentary about alternative medicine with leeches and maggots]
* [http://www.pbs.org/wnet/redgold/basics/bloodlettinghistory.html Document concerning the history of Bloodletting]