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Thursday, February 19, 2009

Leeches

Leech Therapy
They bite, slither, and slide -- and they save fingers and lives.


While the sight of a wriggling, blood-sucking leech may make many people feel queasy, the spineless worms can also help people feel better -- as NATURE's BLOODY SUCKERS shows. The ancient physician's art of using leeches has made a modern medical comeback: the worms help doctors do everything from reattach severed fingers to treat potentially fatal circulation disorders.


Leeches have been used by physicians since ancient times.
Leeches -- which are found all over the world, living mostly in fresh water -- have long had a place in the doctor's medical kit. Five thousand years ago, Egyptian medics believed that letting a leech sip a sick patient's blood could help cure everything from fevers to flatulence. And in medieval Europe, leeches were so closely associated with doctors that physicians were called "leeches" -- and they used millions of the parasites annually to treat patients.

In the 20th century, however, most doctors turned away from the worms, which in nature feed on everything from frogs to alligators. A few physicians, however, saw that leeches might play a special role in certain kinds of surgery, by helping promote blood flow to damaged tissue. That's because when leeches bite a victim, their unique saliva causes blood flow to increase and prevents clotting. As a result, once bitten, victims can bleed for hours, allowing oxygenated blood to enter the wound area until veins re-grow and regain circulation.

The leech is invaluable in microsurgery when faced with the difficulties of reattaching minute veins. Ears have such tiny veins that, in the past, no one was able to successfully reattach them. Then, in 1985, a Harvard physician was having great difficulty in reattaching the ear of a five-year-old child; the tiny veins kept clotting. He decided to use leeches and the ear was saved. This success established leeches in the modern medical world. Since then, leeches have saved lives and limbs, reducing severe and dangerous venous engorgement post-surgery in fingers, toes, ear, and scalp reattachments; limb transplants; skin flap surgery; and breast reconstruction.

Perhaps the best known advocate of medical leeches is Roy Sawyer, an American researcher. Several decades ago, he recognized the potential benefits of "leech therapy" and started one of the world's first modern leech farms. Today, the company -- Biopharm, based in Britain -- provides tens of thousands of leeches every year to hospitals in dozens of countries. Two species are commonly used in leech therapy, which can last for up to 10 days.


Leeches can help promote blood flow to damaged tissue.
Leeches do have their downsides. Sometimes, they slip off patients and reattach themselves in unwanted places. And no matter how helpful, some patients simply can't stomach the thought of a blood-sucking parasite burrowing into their skin. So some scientists have developed a "mechanical leech" that can perform some of the same duties -- without the gross-out factor.

"In the case of the leech in medicine, we think we can improve on nature," says Nadine Connor, a University of Wisconsin at Madison scientist who in 2001 helped develop the mechanical leech. The device, which looks a little like a small bottle attached to a suction cup, delivers an anti-clotting drug to damaged tissue and then gently sucks out as much blood as needed. And, unlike real leeches, the mechanical version is insatiable and can remove as much blood as doctors think is necessary (real leeches drop off when engorged with blood).

"But perhaps the mechanical device's biggest advantage is that it is not a leech," says Connor. "People don't want this disgusting organism hanging on their body. This added psychological stress for both patient and family members compounds an already difficult situation."

Other physicians, however, still swear by the natural wrigglers. Leeches, they say, are a nearly perfect -- and self-reproducing -- surgical tool. And the leech's bite, they add, isn't nearly as bad as its reputation.

Application

Leeches can be used in many applications especially for medical and cosmetic purpose. Traditional use of leeches is by letting the leech to suck blood of the patient’s body to relief symptoms like headache and join pain. Leech oil is known to the local community for enhancing
the sex capability of man. In India, it is used for preventing hair loss. Chinese medicine use leech as and ingredient for various treatments. Modern medicine uses the ingredient extracted from leech to cure blood related diseases. Leeches have been used for medical purposes since over 2000 years ago.
One example is using leeches to suck out the blood in the body to achieve the healing purpose. Today there is a real clinical application in this method; they are of great value to plastic surgeons when venous congestion of skin and muscle flaps is a problem. The leech can suck the blood at the joint where blood is clogged and make it flow again. Leeches today are used in plastic and reconstructive surgery worldwide. There is also successful ongoing research into relieving symptoms of osteoarthritis by using leech. One bigger progress in using leeches in medical field is that they have been approved in America for use in therapy purposes. Live leech are being distributed to various location in the country and also worldwide for use. After sucking the blood, leeches are treated in the same way as other blood treatment procedure that they only can be used on the same patient. This is mainly to prevent the spreading of disease that carried by blood. Other usage of leeches also includes treatment of black eyes. Hirudin, the anti-coagulant from leech can be used in the treatment of inflammation of the middle ear. It is also being developed for experimental use as a systemic anticoagulant, and may prove useful in invitro blood sampling. By extracting the anti-clotting serum from the leech researchers are isolating new pharmaceutical compounds for eventual treatment of heart diseases.
From the history, leech was indispensable in 19th Century medicine for bloodletting, a practice believed to be a cure for anything from headaches to gout. The medicinal leech is getting more popular in modern medicine thanks to the work of Dr. Roy Sawyer, an American scientist who established the world’s first leech farm. Thousands of patients owe the successful reattachment of body parts to technological advances in plastic and reconstructive surgery; at least some of these operations might have failed if leeches had not been reintroduced into the operating room.
The reason for using leeches in surgical procedures is actually very straightforward. The key to success is from what contain in the leech bite, which punctures a wound that bleeds literally for hours. The leech’s saliva contains substances that anaesthetize the wound area, dilate the blood vessels to increase blood flow, at the same time prevent the blood from clotting. Usually the surgeon can get blood to flow in the reattached arteries but not veins. With the venous circulation severely compromised, the blood going to the reattached finger becomes congested; the reattached portion turns blue and lifeless and is at serious risk of being lost. At this time leeches start to play their major role in letting go of the clotting blood. Leech farming is an industry that is getting more popular as more leech usage has been established. One reason is also due to the number of leeches getting lesser in the wild, after the heavy usage of insecticide and pesticide. More researches are on going in discovering the uses of leech that can help us to cure the blood related problem such as heart diseases and also high cholesterol in our body. The role of leech will change from a blood sucking creature that is feared by many people to a great helper in our health.

Leeches

Biology

leech
Illustration: K. Dempsey

Leeches are annelids or segmented worms, and although closely related to the earthworms, are anatomically and behaviourally more specialised.

The bodies of all leeches are divided into the same number of segments (34), with a powerful clinging sucker at each end (although the anterior, or front sucker can be very small). Body shape is variable, but to some extent depends on the degree to which their highly muscular bodies are contracted. The mouth is in the anterior sucker and the anus is on the dorsal surface (top) just in front of the rear sucker.

Leeches usually have three jaws and make a Y-shaped incision. The Australian land leech has only two jaws and makes a V-shaped incision. Australian leeches can vary in size from about 7 mm long to as much as 200 mm when extended.

Different Types

Leeches are grouped according to the different ways they feed. One group (the jawed leeches or Gnatbobdellida) have jaws armed with teeth with which they bite the host. The blood is prevented from clotting by production of a non-enzymatic secretion called hirudin. The land leech commonly encountered by bushwalkers is included in this group.

Jawed scrub leech
Jaw drawings, after M. Stachowitsch The Invertebrates - an Illustrated Glossary

A second group (the jawless leeches or Rhyncobdellida) insert a needle-like protrusion called a proboscis into the body of the host and secrete an enzyme, hemetin which dissolves clots once they have formed. Leeches which live on body fluids of worms and small freshwater snails possess such an apparatus.

A third group, (the worm leeches or Pharyngobdellida) have no jaws or teeth and swallow the prey whole. Its food consists of small invertebrates.

Respiration

Respiration takes place through the body wall, and a slow undulating movement observed in some leeches is said to assist gaseous exchange. Aquatic leeches tend to move to the surface when they find themselves in water of low oxygen content. As a fall in atmospheric pressure results in a small decrease in dissolved oxygen concentrations, rising leeches in a jar of water provided nineteenth century weather forecasters with a simple way of predicting bad weather.

Sense Organs

Sensory organs on the head and body surface enable a leech to detect changes in light intensity, temperature, and vibration. Chemical receptors on the head provide a sense of smell and there may be one or more pairs of eyes. The number of eyes and their arrangement can be of some use in Identification, however to properly identify a leech, dissection is required.

The Rhyncobdellids are capable of dramatic colour changes, and although not an attempt at camouflage, the significance of this behaviour is unknown.

Reproduction

As hermaphrodites, leeches have both male and female sex organs. Like the earthworms they also have a clitellum, a region of thickened skin which is only obvious during the reproductive period. Mating involves the intertwining of bodies where each deposits sperm in the others' clitellar area. Rhyncobdellids have no penis but produce sharp packages of sperm which are forced through the body wall.

Leeches copulating

The sperm then make their way to the ovaries where fertilisation takes place. The clitellum secretes a tough gelatinous cocoon which contains nutrients, and it is in this that the eggs are deposited.

The leech shrugs itself free of the cocoon, sealing it as it passes over the head.

The cocoon is either buried or attached to a rock, log or leaf and dries to a foamy crust. After several weeks or months, the young emerge as miniature adults. Studies show that the cocoons are capable of surviving the digestive system of a duck. Leeches die after one or two bouts of reproduction.

Feeding

Most leeches are sanguivorous, that is they feed as blood sucking parasites on preferred hosts. If the preferred food is not available most leeches will feed on other classes of host. Some feed on the blood of humans and other mammals, while others parasitise fish, frogs, turtles or birds. Some leeches will even take a meal from other sanguivorous leeches which may die after the attack.

Sanguivorous leeches can ingest several times their own weight in blood at one meal. After feeding the leech retires to a dark spot to digest its meal. Digestion is slow and this enables the leech to survive during very long fasting periods (up to several months).

Foraging - How does a leech go about searching for a blood meal?

Leech movement

A hungry leech is very responsive to light and mechanical stimuli. It tends to change position frequently, and explore by head movement and body waving. It also assumes an alert posture, extending to full length and remaining motionless. This is thought to maximise the function of the sensory structures in the skin.

In response to disturbances by an approaching host, the leech will commence "inchworm crawling", continuing in a trial and error way until the anterior sucker touches the host and attaches. Aquatic leeches are more likely to display this "pursuit" behaviour, while common land leeches often accidentally attach to a host.

The Bite

When a jawed leech bites it holds the sucker in place by making its body rigid. Using its semi circular and many toothed jaws like minute saws, it then makes an incision in the skin and excretes a mucous from the nephropores (external openings from the kidney-like organs). This helps the sucker to adhere. A salivary secretion containing the anticoagulant and a histamine floods the wound and the leech relaxes its body to allow the blood to be ingested. This mixture allows the blood to flow and also prevents clotting once inside the leech. A bacterium in the gut of the leech assists the digestion of the blood, and it has been shown that the type of bacterium varies with the type of host on which the leech feeds. The bacterium also prevents growth of other bacteria which may cause the ingested blood to putrefy.

Habitat

Most leeches are freshwater animals, but many terrestrial and marine species occur.

Land leeches are common on the ground or in low foliage in wet rain forests. In drier forests they may be found on the ground in seepage moistened places. Most do not enter water and cannot swim, but can survive periods of immersion.

In dry weather, some species burrow in the soil where they can survive for many months even in a total lack of environmental water. In these conditions the body is contracted dry and rigid, the suckers not distinguishable, and the skin completely dry. Within ten minutes of sprinkling with a few drops of water, these leeches emerge, fully active.

Freshwater leeches prefer to live in still or slowly flowing waters, but specimens have been collected from fast flowing streams.

Some species are considered amphibious as they have been observed in both terrestrial and aquatic habitats.

Uses in Medicine

For over 2000 years, leeches were needlessly applied for many ailments as an adjunct to blood letting. Their use in Europe peaked between 1830 and 1850, but subsequent shortages led to a decline in their use. Today there is a real clinical application in that they are of great value to plastic surgeons when venous congestion of skin and muscle flaps is a problem.

Leeches are treated in the same way as blood products and are reused only on the same patient.

Medical use of leeches also includes treatment of black eyes, and hirudin is used in the treatment of inflammation of the middle ear. Hirudin is also being developed for experimental use as a systemic anticoagulant, and may prove useful in invitro blood sampling.

Repellents

The most common enquiry regarding leeches concerns repellents. It is unknown whether a specific preparation is commercially available but there is a plethora of tried and tested, but unproven leech-protection ideas. These include a lather of bath soap smeared on exposed parts and left to dry, applications of eucalyptus oil, tropical strength insect repellent, lemon juice and impenetrable barriers of socks and pantyhose.

The Wound

The presence of hirudin in the wound following a leech bite may cause oozing to continue for several hours. Although inconvenient, blood loss is not significant.

Gut bacteria can cause wound infection. In the post-operative use of leeches this is closely monitored and dealt with by use of the appropriate antibiotic.

There may also be a delayed irritation and itching after a bite. There appears to be no support for the theory that mouthparts left behind after forced removal of the leech causes this reaction.

Can leeches transmit disease? There is no evidence to suggest that they do. The presence of trypanosomes, (malarial parasites), in the gut of jawless leeches has been noted, but jawed leeches do not appear to be hosts.

Allergy to leech bite has been reported. Medical opinion should be sought, depending on the severity of the reaction.

The leech was indispensable in 19th Century medicine for bloodletting, a practice believed to be a cure for anything from headaches to gout. Leeching was largely abandoned as medical science advanced, only occasionally being called upon to treat bruising and black eyes. However, the medicinal leech is making a comeback in modern medicine thanks in part to the work of Dr. Roy Sawyer, an American scientist who established the world's first leech farm.

Based at Hendy near Swansea, South Wales, Biopharm is home to over 50,000 leeches which are supplied to hospitals and research laboratories around the world.

Thousands of patients owe the successful reattachment of body parts to miraculous technological advances in plastic and reconstructive surgery; at least some of these operations might have failed if leeches had not been reintroduced into the operating room. The appendages reattached include fingers, hands, toes, legs, ears, noses and scalps.

The pioneering use of leeches in modern plastic and reconstructive surgery can be attributed to two Slovenian surgeons, M. Derganc and F. Zdravic from Ljubljana who published a paper in the British Journal of Plastic Surgery in 1960 describing leech-assisted tissue flap surgery (in which a flap of skin is freed or rotated from an adjacent body area to cover a defect or injury). These surgeons credit their own use of leeches to a Parisian surgeon, one Philippe-Frédéric, who reported in 1836 that he had used leeches to restore circulation following reconstruction of a nose.

The rationale behind the use of leeches in surgical procedures is fairly straightforward; nonetheless, it is subject to misunderstanding, even by clinicians. The key to success is the exploitation of a unique property of the leech bite, namely, the creation of a puncture wound that bleeds literally for hours. The leech's saliva contains substances that anaesthetise the wound area, dilate the blood vessels to increase blood flow, and prevent the blood from clotting.

Microsurgeons today are adept at reattaching severed body parts, such as fingers. They usually have little trouble attaching the two ends of the arteries, because arteries are thick-walled and relatively easy to suture. The veins, however, are thin-walled and especially difficult to suture, particularly if the tissue is badly damaged. All too often the surgeon can get blood to flow in the reattached arteries but not veins. With the venous circulation severely compromised, the blood going to the reattached finger becomes congested, or stagnant; the reattached portion turns blue and lifeless and is at serious risk of being lost. It is precisely in such cases that leeches are summoned.





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