Worms are invertebrate (in-VER-te-bret) animals, which means they lack spinal columns (backbones). Worms can cause certain types of parasitic infestation * in humans.
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Diseases and conditions caused by worms are as varied as the types of worms that cause them. Worms that act as parasites * come in thousands of different species, including roundworms, tapeworms, flatworms, flukes, and leeches. The worms may be microscopic, or they may be as long as 9 meters (almost 30 feet).
Some worms cause painful and deforming conditions, while others are barely noticed by the host. Some worm infestations clear up after a short time, while others cause long-term problems that affect many different body organs and may even cause death. Common garden earth-worms do not cause human illness.
Frequent handwashing, good hygiene, good sanitary conditions, and clean water can help prevent worm infections. Prompt diagnosis and treatment by a doctor can help clear up worm infestations.
* infestation occurs when parasites are living on or in the body tissues of a human or other host.
* parasites are creatures that live in and feed on the bodies of other organisms.
The World Health Organization's Division of Control of Tropical
Diseases posts many fact sheets about worm infections at its website.
The U.S. National Institute of Allergy and Infectious Diseases posts a
fact sheet about parasitic roundworm diseases at its website.