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Hirudo medicinalis

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Hirudo medicinalis
CITESAppendix II(CITES)[2]
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Annelida
Clade: Pleistoannelida
Clade: Sedentaria
Class: Clitellata
Subclass: Hirudinea
Order: Arhynchobdellida
Family: Hirudinidae
Genus: Hirudo
Species:
H. medicinalis
Binomial name
Hirudo medicinalis

Hirudo medicinalis,or theEuropean medicinal leech,is one of severalspeciesofleechesused asmedicinal leeches.

Other species ofHirudosometimes also used as medicinal leeches includeH. orientalis,H. troctina,andH. verbana.The Asian medicinal leech includesHirudinariamanillensis,and the North American medicinal leech isMacrobdelladecora.

Medicinal leech populations were reduced significantly in many countries during the 19th century due to the high demand in medical contexts, and remain endangered in many countries today.[3]

Morphology

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The generalmorphologyof medicinal leeches follows that of most other leeches. Fully mature adults can be up to 20 centimeters in length, and are green, brown, or greenish-brown with a darker tone on thedorsalside and a lighterventralside. The dorsal side also has a thin red stripe. These organisms have two suckers, one at each end, called theanteriorandposteriorsuckers. The posterior is used mainly for leverage, whereas the anterior sucker, consisting of thejawandteeth,is where the feeding takes place. Medicinal leeches have three jaws (tripartite) that resemble saws, on which are approximately 100 sharp edges used to incise the host. The incision leaves a mark that is an inverted Y inside of a circle. After piercing the skin, they suck outbloodwhile injecting blood thinners similar toAnophelins;anticoagulants(hirudin).[4]Large adults can consume up to ten times their body weight in a single meal, with 5–15 mL being the average volume taken.[5]These leeches can live for up to a year between feedings.[6]

Medicinal leeches arehermaphroditesthat reproduce bysexualmating, laying eggs in clutches of up to 50 near (but not under) water, and in shaded, humid places. A study done in Poland found that medicinal leeches sometimes breed inside the nests of large aquatic birds, noting that conservation efforts directed at bird habitats may also indirectly help preserve dwindling leech populations.[7]

Range and ecology

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Typical habitat with a large population, Germany

Their range extends over almost the whole ofEuropeand intoAsiaas far asKazakhstanandUzbekistan.The preferredhabitatfor this species is muddy freshwater pools and ditches with plentiful weed growth in temperate climates.

Over-exploitationbyleech collectorsin the 19th century has left only scattered populations,[3]and reduction in natural habitat through drainage has also contributed to their decline. Another factor includes the replacement ofhorses- medicinal leeches' preferred host species - by motor vehicles and mechanical farming equipment, and the provision of artificial water supplies for cattle. As a result, this species is now considerednear threatenedby theIUCN,and European medicinal leeches are legally protected through nearly all of their natural range. They are particularly sparsely distributed inFranceandBelgium,and in the UK there may be as few as 20 remaining isolated populations (all widely scattered). The largest, located atLydd, England,is estimated to contain several thousand individuals; 12 of these areas have been designatedSites of Special Scientific Interest.There are small, transplanted populations in several countries outside their natural range, including the USA. The species is protected under Appendix II ofCITESmeaning international trade (including in parts and derivatives) is regulated by the CITES permitting system.[2]

Medical use

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Beneficial secretions

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Medicinal leeches have been found to secretesalivacontaining about 60 differentproteins.[8]These achieve a wide variety of goals useful to the leech as it feeds, helping to keep the blood in liquid form and increasing blood flow in the affected area. Several of these secreted proteins serve asanticoagulants(such ashirudin),platelet aggregationinhibitors (most notablyapyrase,collagenase,and calin),vasodilators,andproteinaseinhibitors.[9]It is also thought that the saliva contains ananesthetic,[10]as leech bites are generally not painful.

Treatingmastitisof a cattle with leech

Historically

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Acaricatureof a physician prescribing leeches for a weak, bedbound woman

The first recorded use of leech therapy was 3,500 years ago in Ancient Egypt.[11]The next recorded uses of leeches in medicine come in the last few centuries BCE, by the Greek physicianNicanderinColophon[5]and in the ancient Sanskrit textSushruta Samhita.[12]Leech therapy is mentioned a few hundred years later inShennong Bencaojing,a 3rd-century CE book of traditional Chinese medicine.[13]

Medical use of leeches was discussed byAvicennainThe Canon of Medicine(1020s), and byAbd al-Latif al-Baghdadiin the 12th century.[citation needed]

These sources indicated leech therapy for a wide variety of ailments, includingedema,.[12]"blood stasis",[13]and skin diseases.[14]

Earthenware jar for holding medicinal leeches

In medieval and early modern European medicine, the medicinal leech (Hirudo medicinalisand its congenersH. verbana,H. troctina,andH. orientalis) was used to remove blood from a patient as part of a process to balance thehumorsthat, according toGalen,must be kept in balance for the human body to function properly. (The four humors of ancient medical philosophy were blood,phlegm,black bile,andyellow bile.) Any sickness that caused the subject's skin to become red (e.g.feverand 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. Leeches, by removing blood, were thought to help with these kinds of conditions — a wide range which included illnesses likepolioandlaryngitis.[5]Leeches were often gathered by leech collectors and were eventually farmed in large numbers. A unique 19th-century "Leech House"survives inBedale,North Yorkshireon the bank of the Bedale Beck, used to store medicinal leeches until the early 20th century.

Manchester Royal Infirmaryused 50,000 leeches a year in 1831. The price of leeches varied between one penny and threepence halfpenny each. In 1832 leeches accounted for 4.4% of the total hospital expenditure. The hospital maintained an aquarium for leeches until the 1930s.[15]The use of leeches began to become less widespread towards the end of the 19th century.[5]

Current

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Medicinal leech therapy (also referred to asHirudotherapyorHirudin therapy) made an international comeback in the 1970s inmicrosurgery,[16][17][18]used to stimulate circulation in tissues threatened by postoperative venous congestion,[16][19]particularly in finger reattachment andreconstructive surgeryof the ear, nose, lip, and eyelid.[17][20]Other clinical applications of medicinal leech therapy includevaricose veins,muscle cramps,thrombophlebitis,andosteoarthritis,among many varied conditions.[21]The therapeutic effect is not from the small amount of blood taken in the meal, but from the continued and steady bleeding from the wound left after the leech has detached, as well as the anesthetizing, anti-inflammatory, and vasodilating properties of the secreted leech saliva.[5]The most common complication from leech treatment is prolonged bleeding, which can easily be treated, but more serious allergic reactions and bacterial infections may also occur.[5]Leech therapy was classified by the USFood and Drug Administrationas a medical device in 2004.[22]

Because of the minuscule amounts ofhirudinpresent in leeches, it is impractical to harvest the substance for widespread medical use. Hirudin (and related substances) are synthesized usingrecombinanttechniques. Devices called "mechanical leeches" that dispenseheparinand perform the same function as medicinal leeches have been developed, but they are not yet commercially available.[23][24][25][26]

See also

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References

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  1. ^Utevsky S, Zagmajster M, Trontelj P (2014)."Hirudo medicinalis".IUCN Red List of Threatened Species.2014:e.T10190A21415816.doi:10.2305/IUCN.UK.2014-1.RLTS.T10190A21415816.en.Retrieved19 November2021.
  2. ^ab"The CITES Appendices".cites.org.Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).Retrieved2022-01-14.
  3. ^abKutschera U, Elliott J (2014-11-18)."The European medicinal leech Hirudo medicinalis L.: Morphology and occurrence of an endangered species".Zoosystematics and Evolution.90(2): 271–280.doi:10.3897/zse.90.8715.ISSN1860-0743.
  4. ^Rigbi M, Levy H, Eldor A, Iraqi F, Teitelbaum M, Orevi M, et al. (1987). "The saliva of the medicinal leech Hirudo medicinalis--II. Inhibition of platelet aggregation and of leukocyte activity and examination of reputed anaesthetic effects".Comparative Biochemistry and Physiology. C, Comparative Pharmacology and Toxicology.88(1): 95–98.doi:10.1016/0742-8413(87)90052-1.PMID2890494.
  5. ^abcdefWells MD, Manktelow RT, Boyd JB, Bowen V (1993). "The medical leech: an old treatment revisited".Microsurgery.14(3): 183–186.doi:10.1002/micr.1920140309.PMID8479316.S2CID27891377.
  6. ^Lent CM, Fliegner KH, Freedman E, Dickinsont MH (1988)."Ingestive behaviour and physiology of the medicinal leech".Journal of Experimental Biology.137:513–27.doi:10.1242/jeb.137.1.513.PMID3209972.
  7. ^Buczyński P, Tończyk G, Bielecki A, Cichocka J, Kitowski I, Grzywaczewski G, et al. (April 2014)."Occurrence of the medicinal leech (Hirudo medicinalis) in birds' nests".Biologia.69(4): 484–488.Bibcode:2014Biolg..69..484B.doi:10.2478/s11756-014-0329-0.ISSN0006-3088.S2CID255377852.
  8. ^Baskova IP, Zavalova LL, Basanova AV, Moshkovskii SA, Zgoda VG (July 2004). "Protein profiling of the medicinal leech salivary gland secretion by proteomic analytical methods".Biochemistry. Biokhimiia.69(7): 770–775.doi:10.1023/b:biry.0000040202.21965.2a.PMID15310277.S2CID22828659.
  9. ^"Biology".Sangues Medicinales.Ricarimpex.Archived fromthe originalon October 10, 2018.RetrievedNovember 26,2012.
  10. ^Mory RN, Mindell D, Bloom DA (July 2000). "The leech and the physician: biology, etymology, and medical practice with Hirudinea medicinalis".World Journal of Surgery.24(7): 878–883.doi:10.1007/s002680010141.hdl:2027.42/42411.PMID10833259.S2CID18166996.[dead link]
  11. ^"History".Arizona Leech Therapy.Retrieved2023-01-19.
  12. ^abŞenel E, Taylan Özkan A, Mumcuoglu KY (October 2020)."Scientometric analysis of medicinal leech therapy".Journal of Ayurveda and Integrative Medicine.11(4): 534–538.doi:10.1016/j.jaim.2018.11.006.PMC7772485.PMID31289001.S2CID195871696.
  13. ^ab"Võng khan gia tái trung...".www.tmrjournals.com.Retrieved2023-01-19.
  14. ^Montinari MR, Minelli S (May 2022)."From ancient leech to direct thrombin inhibitors and beyond: New from old".Biomedicine & Pharmacotherapy.149:112878.doi:10.1016/j.biopha.2022.112878.PMID35364378.S2CID247833657.
  15. ^Brockbank W (1952).Portrait of a Hospital.London: William Heinemann. p. 73.
  16. ^abWittke-Michalsen E (March 14, 2007)."2: The History of Leech Therapy".In Michaelsen A, Roth M, Dobos G (eds.).Medicinal Leech Therapy.Thieme. pp. 4–12.ISBN978-3-13-161891-7.RetrievedDecember 18,2013.
  17. ^abAltman LK (February 17, 1981)."The doctor's world; leeches still have their medical uses".The New York Times.p. 2.
  18. ^Mumcuoglu KY (2014)."Recommendations for the use of leeches in reconstructive plastic surgery".Evidence-Based Complementary and Alternative Medicine.2014:205929.doi:10.1155/2014/205929.PMC3933224.PMID24653746.
  19. ^Abdelgabar AM, Bhowmick BK (March 2003). "The return of the leech".International Journal of Clinical Practice.57(2): 103–105.doi:10.1111/j.1742-1241.2003.tb10436.x.PMID12661792.S2CID28256939.
  20. ^Frodel JL, Barth P, Wagner J (December 2004). "Salvage of partial facial soft tissue avulsions with medicinal leeches".Otolaryngology–Head and Neck Surgery.131(6): 934–939.doi:10.1016/j.otohns.2004.07.005.PMID15577793.S2CID34041779.
  21. ^"Applications in General Medicine".Sangues Medicinales.Ricarimpex. Archived fromthe originalon March 6, 2013.RetrievedNovember 26,2012.
  22. ^"Product Classification: Leeches, Medicinal".www.accessdata.fda.gov.Retrieved19 August2019.
  23. ^Runwal, Priyanka (December 1, 2022)."Leeches are still used in medicine—yes, really. Here's why".National Geographic.RetrievedJune 18,2024.
  24. ^Salleh A (14 December 2001)."A mechanical medicinal leech?".ABC Science Online.Retrieved29 July2007.
  25. ^Crystal C (14 December 2000)."Biomedical Engineering Student Invents Mechanical Leech".University of VirginiaNews.Archived fromthe originalon 2001-04-14.Retrieved29 July2007.
  26. ^Fox M."ENT Research Group Recognized for Mechanical Leech Project".Otoweb News.University of Wisconsin,Madison, Division of Otolaryngology. Archived fromthe originalon December 11, 2006.RetrievedDecember 16,2013.
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