Hookworm is a type of parasitic roundworm that burrows through the skin, moves through the bloodstream to the lungs, and finally moves into the intestinal tract.

What Is Hookworm?

Hookworm is a type of parasitic * roundworm, known as a nematode (NEH-muh-tode), that has hooked mouthparts. The worm uses these mouthparts to fasten itself onto the intestinal walls of various hosts, including humans. Hookworm larvae (the stage between egg and adult) often enter the body through the skin between the toes in people who go barefoot. Hookworm affects about one-fourth of the world's population, most often in warm, moist areas and in places with poor sanitation.

How Do Hookworms Grow?

Adult hookworms live inside the small intestine of humans and other animals, where they attach to the intestinal wall and feed on the host's blood. Eggs are passed in the host's stools (feces). The eggs hatch into larvae in one to two days under warm, moist conditions out of direct sunlight. The larvae grow in the stools or soil for 5 to 10 days until they become filariform (fuh-LARE-uh-form), or threadlike. During this stage, hookworm can cause infection.

The parasitic hookworm Ancylostoma canium uses its hooked mouthpart to attach to the intestinal wall.

The parasitic hookworm Ancylostoma canium uses its hooked mouthpart to attach to the intestinal wall. 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. CDC.
The United States and the World

In 1902 Dr. Charles W. Stiles (1867–1941) discovered a variety of hookworm indigenous to the United States. At the time, eight hookworms were a serious problem in the southern United States because of the warm, moist climate and poor sanitation conditions, combined with people's habit of going barefoot. Hookworm was called the “germ of laziness” by the popular press of the day.

In 1909 oil magnate John D. Rockefeller (1839–1937) established the Rockefeller Sanitary Commission for the Eradication of Hookworm Disease with the gift of a $1 million grant toward the cure and prevention of hookworm disease. Stiles's work through the commission became a model used in hookworm eradication programs worldwide.

How Is Hookworm Diagnosed and Treated?

The most common symptom of hookworm is anemia * caused by a loss of iron due to blood loss. Other symptoms include lack of appetite, weight loss, diarrhea * , and vague abdominal pain. When the larvae are in the lungs, there may be a dry cough and mild fever. When the larvae burrow into the skin, there may be mild itching and a rash. It is not uncommon, however, for mild infections to show no symptoms at all.

An infection is confirmed in the laboratory by observing eggs in stool samples under a microscope. Medications can be prescribed to treat the infection. Anemia is treated with iron supplements.

Can Hookworm Be Prevented?

The most effective method of prevention is limiting direct contact between infected soil or sand and skin. In areas where hookworm is common or where human feces may be in the sand or soil, people should avoid walking barefoot or touching the soil or sand with their bare hands.

See also Parasitic Diseases: Overview • Roundworm Infection


Books and Articles

Molina, Rachel. “Roundworms Have the Right Stuff.” NASA Science, May 23, 2015. http://science.nasa.gov/science-news/science-at-nasa/2015/23may_roundworms (accessed July 17, 2015).


MedlinePlus. “Hookworm.” U.S. National Library of Medicine. https://www.nlm.nih.gov/medlineplus/ency/article/000629.htm (accessed June 12, 2016).

USAID Neglected Tropical Diseases Program. “Hookworm.” https://www.neglecteddiseases.gov/target_diseases/soil_transmitted_helminthiasis/hookworm (accessed June 12, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30333. Toll-free: 800-311-3435. Website: http://www.cdc.gov (accessed July 17, 2015).

National Institute of Allergy and Infectious Diseases. Office of Communications and Government Relations, 5601 Fishers Lane, MSC 9806, Bethesda, MD 20892-9806. Toll-free: 866-284-4107. Website: http://www.niaid.nih.gov (accessed June 17, 2016).

* parasitic (pair-uh-SIH-tik) refers to organisms such as protozoa (one-celled animals), worms, or insects that can invade and live on or inside human beings and may cause illness. An animal or plant harboring a parasite is called its host.

* anemia (uh-NEE-me-uh) is a blood condition in which there is decreased hemoglobin in the blood and, usually, fewer than normal numbers of red blood cells.

* diarrhea (di-ah-RE-uh) refers to frequent, watery stools (bowel movements).

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)