Hookworm

Hookworm

Hookworm is infestation by a small, round, blood-sucking parasite; commonly causes a rash on the foot, but can also cause cough, pneumonia, and anemia.

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Hookworm Life Cycle

Epidemiology

• An estimated 576-740 million people in the world are infected with hookworm.
• Hookworm was once widespread in the United States, particularly in the southeastern region, but improvements in living conditions have greatly reduced hookworm infections.
• Hookworm, Ascaris, and whipworm are known as soil-transmitted helminths (parasitic worms).
• Together, they account for a major burden of disease worldwide.
• Hookworms live in the small intestine.

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Hookworm

Causal Agents

• Intestinal hookworm disease in humans is caused by Ancylostoma duodenale, A. ceylanicum, and Necator americanus.
• Classically, A. duodenale and N. americanus were considered the two primary intestinal hookworm species worldwide, but newer studies show that a parasite infecting animals, A. ceylanicum, is also an important emerging parasite infecting humans in some regions.
• Occasionally larvae of A. caninum, normally a parasite of canids, may partially develop in the human intestine and cause eosinophilic enteritis, but this species does not appear to reach reproductive maturity in humans.
• Another group of hookworms infecting animals can penetrate the human skin causing cutaneous larva migrans (A. braziliense, A. caninum, Uncinaria stenocephala).
• Other than A. caninum noted above, these parasites do not develop further after their larvae penetrate human skin.

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Hookworm larva

Transmission / spreading

• Hookworm eggs are passed in the feces of an infected person.
• If an infected person defecates outside (near bushes, in a garden, or field) or if the feces from an infected person are used as fertilizer, eggs are deposited on soil.
• They can then mature and hatch, releasing larvae (immature worms).
• The larvae mature into a form that can penetrate the skin of humans.
• Hookworm infection is transmitted primarily by walking barefoot on contaminated soil.
• One kind of hookworm (Ancylostoma duodenale)can also be transmitted through the ingestion of larvae.

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Hookworm egg

Risk factors

• People living in areas with warm and moist climates and where sanitation and hygiene are poor are at risk for hookworm infection if they walk barefoot or in other ways allow their skin to have direct contact with contaminated soil.
• Soil is contaminated by an infected person defecating outside or when human feces (“night soil”) are used as fertilizer.
• Children who play in contaminated soil may also be at risk.

Signs and symptoms

• Itching and a localized rash are often the first signs of infection.
• These symptoms occur when the larvae penetrate the skin.
• A person with a light infection may have no symptoms.
• A person with a heavy infection may experience abdominal pain, diarrhea, loss of appetite, weight loss, fatigue and anemia.
• The physical and cognitive growth of children can be affected.

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CDC Hookworm Treatment Protocol

Diagnosis

• Health care providers can diagnose hookworm by taking a stool sample and using a microscope to look for the presence of hookworm eggs.

Prevention

• Do not walk barefoot in areas where hookworm is common and where there may be fecal contamination of the soil.
• Avoid other skin-to-soil contact and avoid ingesting such soil.
• Fecal contamination occurs when people defecate outdoors or use human feces as fertilizer.

The infection of others can be prevented by not defecating outdoors or using human feces as fertilizer, and by effective sewage disposal systems.

Treatment

• Hookworm infections are generally treated for 1-3 days with medication prescribed by your health care provider.
• The drugs are effective and appear to have few side effects.
• Iron supplements may be prescribed if you have anemia.

Strongyloides Life Cycle

Preventive treatment

• In developing countries, groups at higher risk for soil-transmitted helminth infections (hookworm, Ascaris, and whipworm) are often treated without a prior stool examination.
• Treating in this way is called preventive treatment (or “preventive chemotherapy”).
• The high-risk groups identified by the World Health Organization are preschool and school-age children, women of childbearing age (including pregnant women in the 2nd and 3rd trimesters and lactating women) and adults in occupations where there is a high risk of heavy infections.
• School-age children are often treated through school-health programs and preschool children and pregnant women at visits to health clinics.

Mass drug administration (MDA)

• The soil-transmitted helminths (hookworm, Ascaris, and whipworm) and four other “neglected tropical diseases” (river blindness, lymphatic filariasis, schistosomiasis and trachoma) are sometimes treated through mass drug administrations.
• Since the drugs used are safe and inexpensive or donated, entire risk groups are offered preventive treatment.
• Mass drug administrations are conducted periodically (often annually), commonly with drug distributors who go door-to-door.
• Multiple neglected tropical diseases are often treated simultaneously using MDAs.

School age children

• High-intensity hookworm infections occur among both school-age children and adults, unlike the soil-transmitted helminths Ascaris and whipworm. High-intensity infections with these worms are less common among adults.
• The most serious effects of hookworm infection are the development of anemia and protein deficiency caused by blood loss at the site of the intestinal attachment of the adult worms.
• When children are continuously infected by many worms, the loss of iron and protein can retard growth and mental development.

Hookworm Resources
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