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What is a leech? -

A leech is a kind of worm with a taste for blood. Some 680 species of leech have been described, of which around 100 are marine, 480 freshwater, and the remainder terrestrial.

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How old are leeches? -

These parasitic, segmented worms have been around a long time. The oldest known leech fossils date back 266 million years, around the time of the Permian period.

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A taste for blood -

A leech can live anywhere from two to eight years. Most are sanguivorous, meaning they feed as bloodsucking parasites, or predators, on favorite hosts.

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What's on the menu? -

Given the choice, leeches will dine on invertebrates and other vertebrate hosts, things like fish, reptiles, and mammals. But they're also rather partial to us!

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Mealtime! -

Sanguivorous leeches have been snacking on humans for millennia. And get this: they can ingest several times their own weight in blood during one meal.

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The feeding process -

Most leeches feed by sucking blood from their hosts using their anterior sucker, literally attaching themselves to their meal.

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Get to the point -

Some species, the Amazon leech for example, have a proboscis they insert into their prey from their mouth, as illustrated here.

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Cutting edge -

Others are equipped with strong, multiple tooth-lined jaws, which allow them to cut through flesh with alarming ease.

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Ugly and repulsive -

Leeches are not one of nature's prettiest creatures. And the thought of being bitten by one of these slimy bloodsuckers is repulsive to many, naturally!

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Bloodletting -

But did you know that there's a medical procedure that involves just that? It's called bloodletting, and has been practiced for at least 2,500 years.

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A bloody history -

Bloodletting, or phlebotomy, has its origins in antiquity. The Egyptians, Greeks, and Romans—as well as many other ancient peoples—all used it for medical treatment.

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Theory of humor -

Hippocrates, the father of medicine, swore by the procedure, basing it on the theory of humor described in his Hippocratic Corpus. This maintained that health depended on a balance of the four humors: blood, phlegm, black bile, and yellow bile. Bloodletting using leeches enabled physicians to restore balance if they considered blood was present in excess.

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European medicinal leech -

Bloodletting using leeches became rather fashionable in the Middle Ages. More so after the discovery of Hirudo medicinalis—the European medicinal leech.

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Bloodsucker of choice -

The European medicinal leech was the bloodsucker of choice for physicians. Actually rather attractive, it was gentle to the touch, and possessed a voracious appetite. The species was touted as a cure for all sorts of ailments, including gout, various skin diseases, and even mental illness.

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Leech therapy -

Soon, bloodletting had been redescribed as leech therapy. Some physicians overstepped the mark, though, when insisting that leeching could cure more serious disorders such as tuberculosis and even cancer.

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A weighty issue -

Maximilian I, Holy Roman Emperor, was hoodwinked into believing that a spot of leech therapy could help him lose weight. Instead, he ended up suffering blood loss.

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Sucking the life out of the medicinal leech -

In the 19th century, demand for the European medicinal leech nearly drove the species to extinction. Leech mania was sweeping across Europe, endangering this odd-looking but highly prized creature.

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Leech collecting -

Leeching created employment. A leech collector, or leech gatherer, was someone who waded through muddy, swampy water attracting leeches to their bare legs and arms.

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Another source of bait -

Other methods of finding leeches was to lead an old horse through a bog or marsh using its worn out legs as bait.

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The arrival of hirudiculture -

The commercial value of leech farming wasn't lost on savvy entrepreneurs. Rather than pay someone to wade through a pond, why not instead custom create your own reservoirs and canals in an artificial environment? A new name sprang up to describe this nascent method of cultivation: hirudiculture.

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Bloodletting, à la leech -

As the 19th century progressed so too did the desire for bloodletting, à la leech. In France, famed physician François-Joseph-Victor Broussais (1772–1838) claimed that all ills, cancer and smallpox included, were the result of inflammation, which bleeding could cure. His word was such that, in 1833, France imported over 40 million medicinal leeches. The tiny critter was truly under siege.

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Keeping a lid on things -

Fancy and elaborate leech jars were commissioned by pharmacists everywhere, a sure sign that your local apothecary was no sucker when it came to advertising their business!

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The leech makes America -

Meanwhile, leech mania had crossed the Atlantic. Demand for the leech, a non-native species in America, was so high that the US government ended up offering a reward to anyone who successfully raised European leeches on domestic soil.

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Almost extinct -

By the late 19th century, European medicinal leech numbers had been decimated. So much so that physicians reverted to bleeding using more conventional, artificial methods.

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Advances in blood transfusion -

By the early 20th century, technical advances in blood transfusion procedures largely did away with the need for leeching. The demise in humoral theory was also a factor in its cessation.

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Leeches for sale -

Leeches were still used on an occasional basis, as this 1935 photograph of a British pharmacist holding a bowl of the worms clearly illustrates.

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Leech therapy makes a comeback -

In the 1980s, the leech made somewhat of a comeback. Physicians had always appreciated the species' place in medical history and once again started using the worms, often as a component in major operations. Buy why?

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Full of protein -

One active component of leech saliva is a small protein, hirudin. It's widely used as an anti-inflammatory and anticoagulant drug to treat blood-clotting disorders.

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An approved medical device -

In 2004, the United States Food and Drug Administration approved leeches as a medical device to relieve congested veins and restore blood flow in compromised skin grafts.

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The physician's friend -

Today, leeches are used widely in modern medicine to treat a range of chronic and life-threatening abnormalities, such as cardiovascular problems, cancer, metastasis, and infectious diseases.

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The changing face of leech therapy -

And this humble if not handsome worm has also found a place in plastic surgery, where it's used for cosmetic purposes.

Sources: (National Center for Biotechnology Information) (Britannica) (National Geographic) (Medical News Today) (BBC) (Healthline) 

See also: The most bizarre plastic surgeries ever

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