Hookworm

Definition

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 types also occur in animals.

Hookworm disease is widespread in the moist tropics and subtropics, and it affects over 1 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.

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

After traveling up the windpipe, 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.

Symptoms

• Abdominal discomfort
• Blood in the stool
• Bloody sputum
• Cough
• Diarrhea
• Fatigue
• Fever
• Gas
• Itchy rash
• Loss of appetite
• Nausea, vomiting
• Pallor

Note: There are often no symptoms.

Signs and tests

Tests that can help diagnose the infection include:

• Complete blood count (CBC) with differential
• Stool ova and parasites exam

This disease may also alter the results of a D-xylose absorption test.

Treatment

The goals of treatment are to:

• Cure the infection
• Treat complications of anemia
• Improve nutrition

Parasite-killing medications such as albendazole, mebendazole or, pyrantel pamoate are usually prescribed. Ivermectin, used for other worm infections, does not work for hookworm infections.

Symptoms and complications of anemia are treated as they arise. The doctor will likely recommend increasing the amount of protein in your diet.

Expectations (prognosis)

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

Complications

• Anemia
• Severe protein loss with fluid build-up in the abdomen (ascites)
• Other nutritional deficiencies

Calling your health care provider

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

Prevention

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

References

Kazura JW. Nematode infections. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 378.