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Hookworm Infection

  • Hookworm Disease

Definition

A hookworm is a type of roundworm (nematode) called Necator americanus. This parasite causes intestinal infection in animals and humans. It is very common. In fact, about one-fifth of the world's population is infected with hookworms.

What is going on in the body?

Hookworm eggs need warm, moist soil in order to develop into larvae. Humans can acquire the parasite by coming in contact with contaminated soil, often by walking with bare feet. The worms penetrate the skin, enter the bloodstream, and are carried to the lungs. From there, they travel up the airway to the mouth, are swallowed, and sent to the small intestine.
Once in the small intestine, the worms attach themselves to the intestinal wall. It is there that the females will lay their eggs into the fecal stream. These eggs, if passed into the soil, will begin the life cycle again.

Risks

What are the causes and risks of the infection?

Hookworm is most common in warm, moist places where sanitation is poor. Transmission usually occurs through contaminated soil. It is due either to a lack of sanitary facilities or to the use of human manure as fertilizer. Infection can occur when foods contaminated with hookworm cysts are eaten.

Prevention

What can be done to prevent the infection?

Wearing shoes in high-risk areas can help prevent a hookworm infection. Treatment of all infected individuals is important. Screening and treatment of high risk individuals will help decrease disease. The ultimate prevention involves proper disposal of human feces.

Diagnosed

How is the infection diagnosed?

Hookworm is diagnosed by examining a stool specimen. Eggs will be seen in a person infected with the adult worm. Sometimes adult worms may be found in the person's stool or vomit. Chest x-rays may reveal signs of the migration into the lungs. A complete blood count, or CBC, may show anemia.

Long Term Effects

What are the long-term effects of the infection?

A hookworm infection can cause iron deficiency anemia and low levels of protein in the blood can occur if blood is lost through intestinal bleeding. In children, slow growth, heart failure, and widespread tissue swelling may result from the blood loss.

Other Risks

What are the risks to others?

A person who excretes hookworm eggs and does not properly dispose of his or her stool puts others at risk for hookworm infection.

Treatments

What are the treatments for the infection?

Hookworm is treated with albendazole (i.e., Albenza) or pyrantel pamoate (i.e., Antiminth). These medications are taken by mouth for 1 to 3 days. If anemia is present, iron supplements may be given to correct the anemia.

Side Effects

What are the side effects of the treatments?

Side effects of the medications used to treat hookworm include:
  • diarrhea
  • abdominal distress
  • headache
  • dizziness
  • fever
  • rash
Side effects of iron supplements include constipation.

After Treatment

What happens after treatment for the infection?

After treatment, a person's stool should be check again for hookworm infection. If eggs are still present, treatment should be repeated.

Monitor

How is the infection monitored?

If symptoms of a hookworm infection return, the stool should be rechecked.

Sources

Harrison's Principles of Internal Medicine, 1998, Fauci et al.

Tierney, Lawrence, editor, "Current Medical Diagnosis and Treatment, 39th edition", 2000

The Merck Manual of Medical Information, 1997

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