Hookworm Infection

What is hookworm?

Hookworm is an intestinal parasite of humans that usually causes mild diarrhea or cramps. Heavy infection with hookworm can create serious health problems for newborns, children, and persons who are undernourished. Hookworm infections occur mostly in tropical and subtropical climates and are estimated to infect about 1 billion people -- about one-fifth of the world's population.

Where are hookworms commonly found?

One of the most common species, Ancylostoma duodenale (an-cy-CLO-sto-ma doe-AH-den-al), is found in southern Europe, northern Africa, northern Asia, and parts of South America. A second species, Necator americanus (ne-KAY-tor am-er-i-CON-us), was widespread in the southeastern United States early in this century. The Rockefeller Sanitary Commission was founded in response, and hookworm has been largely controlled since.

How do I get a hookworm infection?

Direct contact with contaminated soil, generally through walking barefoot, or accidentally swallowing contaminated soil, can cause infection.

Hookworms have a complex life cycle that begins and ends in the small intestine, but also requires warm, moist, shaded soil. These barely visible larvae penetrate the skin, are then 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 stool. If the eggs reach soil and conditions are right, they will hatch, molt, and develop into infective larvae again after 5 to 10 days.

Who is at risk?

People who have direct contact with soil that contains human feces (stool) in regions where hookworm is common are at high risk of infection. Children -- because they play in dirt and often go barefoot -- are at particularly high risk. Since transmission of hookworm infection requires development of the larvae in soil, hookworm cannot be spread person to person. Contact among children in institutional or child care settings should not increase the risk of infection.

What are the symptoms of hookworm?

Itching and a rash at the site of exposure are usually the first signs of infection. These occur when the larvae penetrate the skin. While light infections may cause no symptoms, heavy infection can cause abdominal pain, diarrhea, loss of appetite, and weight loss.

Can a hookworm infection cause any serious health problems?

Yes. The most serious results of hookworm infection are the development of anemia and protein deficiency caused by blood loss. When children are continuously infected by many worms, the loss of iron and protein can retard growth and mental development, sometimes irreversibly. Hookworm infection can also cause tiredness, difficulty breathing, enlargement of the heart, and irregular heartbeat. Sometimes hookworm infection is fatal, especially among infants.

What should I do if I think I have a hookworm infection?

Visit your health care provider. Infection is diagnosed by identifying hookworm eggs in a stool sample.

What is the treatment for hookworm?

In countries where hookworm is common and reinfection is likely, light infections are often not treated. In the United States, hookworm infections are generally treated for about 3 days with medication prescribed by your health care provider. The drugs are effective and appear to have few side effects. For children under the age of 2, the decision to treat should be made on an individual basis.

Another stool exam should be repeated 1 to 2 weeks after therapy. If the infection is still present, treatment will be given again. Iron supplements will be ordered if you have significant anemia.

How can I prevent hookworm?

No vaccine is available yet, but you can help prevent infection through the sanitary disposal of human feces. In areas where hookworm is common or there is fecal contamination of the soil, do not walk barefoot or contact the soil with bare hands.

For more information:

  1. Bundy DAP. Is the hookworm just another geohelminth? In: Hookworm Disease, Schad GA, Warren KS, eds. London and Philadelphia: Taylor and Francis1990:147-64.

  2. Hotez PJ, Pritchard DI. Hookworm infection. Scientific American 1995 June:68-74.

  3. Roche M, Layrisse M. The nature and causes of 'hookworm anemia' Am J Trop Med Hyg 1966:15;1030-1100.

  4. Schad GA, Warren KS. Hookworm disease: current status and new directions. London: Taylor and Francis, 1990.

This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

Division of Parasitic Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention

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URL: http://www.cdc.gov/ncidod/dpd/hookworm.htm