Hookworm

An intestinal parasite that usually causes diarrhea or cramps. Heavy infestation with hookworm can be serious for newborns, children, pregnant women, and persons who are malnourished. Hookworm infections occur mainly in tropical and subtropical climates and affect about 1 billion people — about one-fifth of the world's population. One of the most common species of hookworm, Ancylostoma duodenale, is found in southern Europe, northern Africa, northern Asia, and parts of South America. A second species, Necator americanus, was once widespread in the southeastern US early in the 20th century. Hookworms have a complex life cycle that begins and ends in the small intestine. Hookworm eggs require warm, moist, shaded soil to hatch into larvae. These barely visible larvae penetrate the skin (often through bare feet), are carried to the lungs, go through the respiratory tract to the mouth, are swallowed, and eventually reach the small intestine. This journey takes about a week. In the small intestine, the larvae develop into half-inch-long worms, attach themselves to the intestinal wall, and suck blood. The adult worms produce thousands of eggs. These eggs are passed in the feces (stool). If the eggs contaminate soil and conditions are right, they will hatch, molt, and develop into infective larvae again after 5 to 10 days. Hookworm infection is contracted from contact with soil contaminated by hookworm, by walking barefoot or accidentally swallowing contaminated soil. Children — because they play in dirt and often go barefoot — are at high risk. Since transmission of hookworm infection requires development of the larvae in soil, hookworm cannot be spread person to person. Chronic heavy hookworm infection can damage the growth and development of children. The loss of iron and protein retards growth and mental development, sometimes irreversibly. The first signs of hookworm infection are itching and a rash at the site where the larvae penetrate the skin. These signs may be followed by abdominal pain, diarrhea, loss of appetite and weight loss, and anemia. Hookworm can also cause difficulty breathing, enlargement of the heart, and irregular heartbeat. Hookworm infection have been known to be fatal, particularly in infants.

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Common name for bloodsucking nematodes of the family Ancyclostomatidae, chiefly members of the genera Ancylostoma (the Old World h.), Necator, and Uncinaria, and including the species A. caninum (dog h.) and N. americanus (New World h.).

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hook·worm 'hu̇k-.wərm n

1) any of several parasitic nematode worms of the family Ancylostomatidae that have strong buccal hooks or plates for attaching to the host's intestinal lining and that include serious bloodsucking pests

2) ANCYLOSTOMIASIS

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n.

either of two nematode worms, Necator or Ancylostoma, which live as parasites in the human intestine. Both species, also known as the New and Old World hookworms respectively, are of great medical importance (see hookworm disease).

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hook·worm (hookґwurm″) any nematode of the family Ancylostomatidae. See also hookworm disease, under disease.