Hookworm, a roundworm that lives as a parasite in the intestines of man and other animals. The hookworm is white and less than 1/2 inch (13 mm) long. Its mouth has cutting plates with which it attaches itself to the intestinal wall of its host. The worm drains blood from the intestinal wall, causing hookworm disease, common in tropical and subtropical areas throughout the world. The disease produces abdominal pain and iron-deficiency anemia. In children it is a frequent cause of fluid retention and stunted growth.

The hookwormThe hookworm lives as a parasite in the intestines of animals.

The hookworm larvae live in moist soil. They enter the body by burrowing through the skin. They are usually contracted by walking barefoot on contaminated soil. Once in the body, the larvae are carried by the blood to the lungs. They then pass into the throat and are swallowed, thus reaching the intestines. Here the female hookworm lays about 30,000 eggs a day. These pass from the body as waste, hatching into larvae on the ground in one or two days.

The disease is controlled today by drugs such as tetrachlorethylene and by improved sanitation.

The common American hookworm is Necator americanus; Old World, Ancylostoma duodenale. Both belong to the family Ancylostomidae of the roundworm phylum, Nematoda.