Question of the Week
July 5, 2004


Leeches are parasites.

"par*a*site: An organism that grows, feeds, and is sheltered on or in a different organism while contributing nothing to the survival of its host."

While the leeches you find in the creek behind your house may be parasites, researches have discovered that some, in more controlled environment,s can be used to improve the health of the host.

"February 1, 1995
Using Leeches as Bait to Go Fishing for New Anticlotting Drugs...
When you cut yourself, you need to clot so that you don't bleed to death. However, sometimes too much clotting leads to serious trouble. For instance, heart attacks are caused by blood clots in the heart and strokes are caused by blood clots in the brain. Triggering clotting in humans is very complex, making sure our blood clots when it should, but not when it shouldn't.... The blood sucking creatures such as leeches, ticks, vampire bats, mosquitoes, snakes, and others have successfully adapted to feeding on mammals by shutting down the clotting process of the 'victim.'...Perhaps the best understood of all the bloodsucking animals is the leech...."

Using leeches to help the sick is nothing new.

"Since the Golden Age of Greece, leeches have been famed for their bloodsucking ability. In fact, during the middle ages of Europe through the early to mid-nineteen hundreds, they were used for medicinal purposes. Today, though it is rare, they are still used to reduce blood volume or control bleeding in some patients....The American medicinal leech, Macrobdella decora, has been found in several farm ponds in Kentucky. This leech has a large, round mouth that also functions as a sucker to hold on to the host. Jaws around the mouth opening hold many fine, conical teeth. Wounds produced when bloodsucking leeches attach to humans or livestock will bleed for a while after the leech is removed or drops. An enzyme secreted by the leech keeps blood from coagulating as it feeds."

Though the practice of using leeches has been around for centuries, their uses are far more specific--and more understood--today, in 2004.

"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...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."

Just last month:

"WASHINGTON (AP) -- The government has lent its seal of approval to a marketing an age-old medical device -- leeches. The Food and Drug Administration said Monday that Ricarimpex SAS, a French firm, is the first company to request and receive FDA clearance to market the bloodsucking aquatic animals as medical devices. Leeches are already widely used in American hospitals...FDA reports that leeches can help heal skin grafts by removing blood pooled under the graft and restore blood circulation in blocked veins by removing pooled blood....In considering the Ricarimpex application, FDA said it analyzed the use of leeches in medicine, evaluated safety data provided by the
firm and studied how the leeches are fed, their environment and the personnel who handle them."

Leeches are still parasites, and those you find in the wild should still be treated as such. Leeches have been approved as medical devices to be used by doctors. They would fall into the category of: Don't try this at home.

"Although scientists have found many medicinal applications and uses for leeches, they can be a nuisance. In 1799, soldiers serving under Napoleon marched from Egypt across the Sinai Peninsula to Syria. They drank water from any source they could find, including waters contaminated by leeches. As a result many problems occurred when the leeches attached to the insides of the soldiers noses, mouths, and throats. Once attached, the leeches began to gorge on blood and enlarge. Many of the soldiers died from suffocation due to the enlarged leeches in the air passages. In addition, other soldiers died from excessive blood loss."

The same qualities that make leeches bothersome parasites also make them useful to the medical community.

Questions of the Week:
In what ways can scientists and doctors turn negative side effects for some into positive results for others? What have we learned by observing the characteristics of leeches? What characteristics naturally found in other organisms are scientists hoping to reproduce to benefit humans? What characteristics have you observed that you think they should be researching--if they are not already?

Please email me with any ideas or suggestions.
Note: Due to increasing amounts of SPAM sent to this account, please include "QOW" in the subject line when sending me email.

I look forward to reading what you have to say.

Health Community Coordinator
Access Excellence @ the National Health Museum

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