Humphrey Bogart had more than a few memorable lines.

Though “Here’s looking at you, kid” is likely the most remembered and repeated, Bogart uttered another more obscure line that almost everyone, except a helminthologist, would agree with. In The African Queen, he griped, “If there is anything in the world I hate, it‘s leeches — filthy little devils!”

Helminthologists are those who study worms, and they would likely disagree.

Love them or hate them, leeches are here to stay. As members of the phylum Annelida, they are related to earthworms, and number more than 650 species worldwide. Leeches live in marine and freshwater environments and can even be found on land. They also reside in Elizabeth’s Pond at Felix Neck, where one was recently found by a student during a third grade field trip to the sanctuary. 

Leeches are interesting for a variety of reasons. They have 32 simple brains or ganglia, they care for their young (one species even carries their offspring in a pouch like a kangaroo), they are hermaphrodites, and leeches have up to 300 teeth in three distinct jaws.

But, of course, the most intriguing thing about leeches is the fact that some species are sanguivorous, meaning that they feed on blood.

Blood sucking leeches have mingled with humans throughout history. As pests and as medicine, leeches have been interacting with us for centuries. Egyptian hieroglyphics depict leeches feeding on humans, and Sanskrit writings note that leeches are an effective treatment for snake bites. The Greeks prescribed these worms to relieve the pain of headaches, and during the second century, noted physician Galen observed that leeches would “reduce plethoras,” an excess volume of blood in the body.

The word leech comes from the Anglo Saxon root loece or laece, which means “to heal.” Leeches were employed for “bloodletting” or “breathing a vein” to remove bad blood and rid the body of evil spirits. This method of healing did not always work. Molière observed that “nearly all men die of their remedies and not of their illnesses.”  

There have been some noteworthy patients that believed in the value of medicinal leeches. Poet Lord Byron, Soviet dictator Joseph Stalin, and writer James Joyce all took advantage of leech treatments. Some say that George Washington died from an over-application of leeches by his physicians during his final illness; others say it was the fault of his physicians themselves who were bleeding him with surgical instruments. In either case, it’s easy to see why “leech” was, in Shakespeare’s time, a synonym for “doctor.”

Leeches are still used medicinally. In 2004, the FDA permitted the leech species Hirudo medicinalis for use as a medical device. It is only the second living creature approved as such. Of course, this begs the question of what was the other FDA-approved live animal treatment. That would be maggots, for use on open wounds to consume dead tissues. But back to the bloodsuckers.

When a leech bites with its three jaws, a sawing action helps it to break through your (or another animal’s) skin. You won’t feel a thing, since leech saliva has a natural anesthetic that makes the incision almost painless. The leech will stay attached to its prey for up to one hour and ingest up to 10 times its body weight in blood. After a feeding, the leech is really full (burp) and can go for up to three years without another blood meal. If a leech is used medicinally, the patient must be monitored after treatment as the wound can continue to bleed for up to ten hours, often causing more blood loss than the original leech treatment.

Today, the most common condition that would require the use of leech therapy is reattachment surgery. Leeches are placed near the site of a reattached limb or tissues to establish artificial circulation. Ten to twelve leeches are recommended for finger reattachment, and several hundred are needed to replace a scalp. It is no surprise then that businesses have sprung up around leech husbandry to produce a safe and available supply of these blood sucking beasts. As Bogie would have said, it looks like “the beginning of a beautiful friendship.”

Whether you are intrigued or disgusted by the leeches in our lives, there is one thing that we all can agree upon. Leeches suck.


Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown.