Hookworm disease is one of the most common parasitic roundworm infections of the intestines. This disease is widespread in tropical and subtropical countries where people may defecate on the ground and where the soil moisture is most favorable for hookworm eggs to develop into larvae (immature worms).

The World Health Organization estimates hookworm disease affects 740 million people worldwide. Once a big problem in the southeastern United States, hookworm disease is now largely controlled in this country.


The parasitic roundworm, known as hookworm, causes hookworm disease. Necator americanus is the most common type of hookworm that causes infection in the United States.

  • Hookworm eggs are passed in human feces onto the ground where they develop into infective larvae (immature worms).
  • When the soil is cool, the larvae crawl to the nearest moist area and extend their bodies into the air.
  • The larvae stay in the soil—waving their bodies to and fro—until they come into contact with human skin, usually when stepped on by a bare foot, or until they are driven back into the ground by the heat.


You can get hookworms by walking barefoot over contaminated soil. In penetrating your skin, the hookworm larvae (immature worms) may cause an allergic reaction. It is from the itchy patch at the place where the larvae entered your body that the early infection came to be known as "ground itch."

Once larvae have broken through your skin, they enter your bloodstream and are carried to your lungs. Unlike ascarids, another form of parasitic roundworm, hookworms do not usually cause pneumonia.

The larvae migrate from your lungs to your windpipe and are then swallowed and carried back down to your small intestine.


Diarrhea sometimes starts as the worms mature in your intestines and before eggs appear in the stool, particularly if you have never been infected by hookworms. During this stage of the disease you may have other symptoms, such as barely noticeable abdominal pain, intestinal cramps, colic, and nausea.

Scientists have learned that people in good health and on a diet containing adequate amounts of iron can tolerate the presence of these worms in small or moderate numbers without any symptoms.

In chronic (lasting a long time) hookworm infections, if the number of parasites becomes great enough, you can develop serious anemia (low red blood cell count). This is due to blood loss from the worms attaching themselves to the intestines and sucking the blood and tissue juices. When this situation is combined with poor nutrition, pregnancy, or malaria, the anemia can be severe.


A laboratory worker will examine your stool specimens to look for and count the number of eggs that may be there.


If the number of hookworm eggs in your intestines is large enough—more than 2,000 eggs per gram of stool—your healthcare provider will assume that the infection may cause anemia and start treating you.

Once you have been diagnosed with hookworm disease, your healthcare provider may prescribe medicine, such as mebendazole or albendazole. You might also be given an iron supplement with this treatment.


If you are in an area where hookworm disease is common, or where human feces may be in the soil or sand, you

  • Should not walk barefoot on the soil or sand
  • Should not touch the soil or sand with your bare hands


NIAID-supported researchers are conducting basic and clinical research on the prevention, control, and treatment of a variety of parasitic diseases, including some caused by parasitic roundworms. This includes possible new treatments with bacterial crystal proteins.

Source: National Institutes of Health; National Institute of Allergy and Infectious Diseases, NIAID

This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 5/12/2011…#14072