this is your brain on leeches

Maggot therapy is an example of a medical approach called biotherapy--the use of living animals to aid in medical diagnosis or treatment. Leeches are another example.

In ancient times, leeches were used to treat everything from headaches to ear infections to hemorrhoids. Historians think Egyptians used leech therapy 3,500 years ago. The treatments were back in vogue during the Middle Ages, and again in the 1800s.

Nowadays, leeches are routinely used to drain blood from swollen faces, limbs and digits after reconstructive surgery.

They are especially useful when reattaching small parts that contain many blood vessels, like ears, where blood clots can easily form in veins that normally drain blood from tissues. If the clots are severe, the tissues can die -- drowned in the body's own fluid -- because they are deprived of oxygen and other vital nutrients.

Scientists are also looking at using leeches to treat other ailments. Studies led by Andreas Michalsen, a researcher at the University of Duisburg-Essen in Germany, suggests leech therapy may lessen the pain and inflammation associated with osteoarthritis, a debilitating disease where bones can grind against one another because the cartilage has been worn down.

Maggots and leeches are so effective that the FDA last year classified them as the first live medical devices. The treatments can be relatively inexpensive, according to the National Institutes of Health. A container of 500-1,000 disinfected maggots last year cost $70.

Scientists have not figured out exactly how either critter works, but quite a bit is known. Maggots eat dead and infected tissue and other infectious organisms, which are later killed in maggots' guts. They secrete enzymes that break down dead tissue, turning it into a mush they can then slurp up.

Leech saliva is made up of a potent cocktail of more than 30 different proteins that, among other things, helps to numb pain, reduce swelling and keep blood flowing.

Patients are rarely repulsed by the leeches and instead take a morbid interest in the creatures. "They feel sympathy for the leeches," he said.