Hookworm is a roundworm infestation affecting the small intestine and lungs. The worms are about 1/2 inch long.

Causes, incidence, and risk factors

The disorder is caused by infestation with the roundworms Necator americanus, Ancylostoma duodenale, Ancylostoma ceylanicum, or Ancylostoma braziliense. The first two occur in humans only. The last two types also occur in animals.

Hookworm disease is widespread in the moist tropics and subtropics, and it affects over one billion people worldwide. In developing nations, the disease indirectly causes the death of many children by increasing their susceptibility to other infections that could normally be tolerated.

There is very little risk of contracting the disease in the U.S. because of advances in sanitation and control of wastes. Hookworm infection in the U.S. is most probable in the southeast.

The larvae (immature form of the worm) penetrate the skin, where an itchy rash called ground itch may develop. They migrate to the lungs via the bloodstream, enter the airways and cause coughing.

After traveling up the bronchi, the larva are swallowed. When the larvae are swallowed, they infect the small intestine and develop into adult worms. Adult worms and larvae are excreted in the feces.

Most people have no symptoms once the worms enter the intestines. However, iron deficiency anemia caused by loss of blood may result from heavy infestation.


  • Itchy rash  
  • Cough  
  • Fever  
  • Bloody sputum  
  • Loss of appetite  
  • Nausea, vomiting  
  • Diarrhea  
  • Abdominal discomfort  
  • Increased gas production  
  • Pallor  
  • Fatigue  
  • Eggs and blood in the stool

Note: There are often no symptoms.

Signs and tests

  • A stool ova and parasites exam will demonstrate the infection.  
  • This disease may also alter the results of a D-xylose absorption test.


The objective of treatment is to cure the infestation, to treat complications of anemia, and to improve nutrition. Parasite-killing medications such as mebendazole or albendazole are usually prescribed. Ivermectin, used for other worm infections, is not effective for hookworm.

Symptoms and complications of anemia are treated as they arise. There is often a recommendation made to increase the amount of protein in the diet to improve nutrition.

Expectations (prognosis)
Complete recovery occurs if treatment is given before serious complications develop. The infection is easily eradicated with treatment.


  • Anemia  
  • Severe protein loss with ascites

Calling your health care provider
Call for an appointment with your health care provider if symptoms of hookworm infection develop.

Improvement in sanitation measures in developing countries is necessary for prevention of infection.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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