Worms That Bite Humans

Worms -- bite people? Yes, and some can eat humans alive. Some kinds of worms will bite to eat; others sting with hairs to defend themselves. Some can live and move inside you. Based on such characteristics, some have even been used in medicine for thousands of years -- and are still used today!

Some worms bore through humans in their life cycle. Hookworm larva enter through skin, usually bare feet, and travel through the lymphatic system into the lungs. They ride swallowed phlegm to live in the intestines. They attach to the gut and suck blood, laying thousands of eggs daily. Roundworms follow a similar course, eating partly digested food before boring through the gut wall to catch that same lung ride back to the intestines. They lay hundreds of thousands of eggs daily.

Leeches are the best-known parasitic worms. They don't bite with their mouths, though -- they have separate, three-bladed jaw structures that cut through skin, and the nearby mouth sucks up the blood. In one meal, they can take in 10 times their weight in blood. They secrete anticoagulants so the blood keeps flowing, and it won't clot in their gut. That's why a bite wound from a leech will continue to bleed after the leech is gone.

For centuries, leeches have been used all around the world in bloodletting. The practice faded in the 19th century, but it's still used in some cases, such as draining excess blood from reattached body parts. Maggots will clean wounds of dead tissue, but they leave live tissue alone. Practiced since the times of the Mayas, this is called biodebridement. It's beginning to see more use, because more and more bacteria are becoming resistant to antibiotics.