Hookworm in Humans: Signs, Transmission, Prevention

Hookworm is an intestinal parasite that affects more than half a billion people globally. The worms live in the small intestines of those who are infected.

Once widespread in the United States, hookworm infections now disproportionately impact poor areas with limited access to sanitation and medical care. The worm's larvae live in contaminated soil, primarily infecting people by burrowing through the bottoms of their bare feet.

Though a safe and effective treatment is available, there are an estimated 576–740 million people currently infected with hookworm worldwide, making it one of the most common neglected tropical diseases impacting humans.

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While most people with hookworm infections don't have any symptoms, long-term infections can cause lifelong consequences for children, including iron deficiency anemia, protein malnutrition, subsequent growth stunting, and decreased cognitive capacity.

This article will cover the signs and symptoms of a hookworm infection, how it's transmitted, treatment measures, and more.

Symptoms and Signs

Not everyone infected with hookworm will get symptoms. When they do, it’s often itchiness or a localized rash that occurs when the larvae penetrate the skin (typically on the bottom of the foot).

Those heavily infected, however, might experience:

• Fatigue
• Diarrhea
• Weight loss
• Lack of appetite
• Abdominal pain
• Anemia

While most people who are infected don't experience any symptoms at all, the disease can cause serious damage if left untreated—especially for pregnant women and young children.

The worms feed on blood, resulting over time in internal blood loss, malnutrition, and anemia. As noted, the long-term impact can lead to serious consequences for children's physical growth and cognitive development.

Transmission

Two types of hookworms infect humans: Ancylostoma duodenale and Necator americanus.

The adult and larvae stage of the worms live in the human intestine and can spread through contaminated soil.

There are two primary ways people become infected with hookworms: skin-to-soil and ingestion through contaminated food or water sources.

Animals vs. Humans

Animal hookworms, like the ones in pet cats and dogs, are a different type than the hookworms transmitted by humans.

It is possible to be infected by animal hookworm and develop a skin condition called cutaneous larva migrans. This causes a raised, red track on the skin that can be itchy.

However, animal hookworm larvae usually don't survive more than six weeks in humans. Signs and symptoms usually resolve without treatment.

The Life Cycle of the Hookworm

The life cycle of the hookworm is similar to those of other intestinal parasites:

• The eggs of the worm are present in infected individuals’ feces.
• People defecate out in the open (rather than in a toilet or latrine) or the stool is collected to use as fertilizer, so the eggs get into the soil.
• Over time, the eggs hatch and release larvae, which mature.
• If you come into contact with the soil, the larvae penetrate your skin to get inside your body. Or you may eat food or drink water that has been contaminated with eggs.
• The larvae make their way to the intestines, where they mature into adults and lay eggs, continuing the cycle.

Risk Factors

Risk factors for hookworm include living in warm, moist climates where sanitation is poor. In particular, it occurs where humans defecate outside or where human feces is used as fertilizer.

Diagnosis

Diagnosing hookworm is a relatively straightforward and simple process. Healthcare providers take a stool sample and look for hookworm eggs under a microscope.

Because it can be tough to spot the eggs if the infection is light, the CDC recommends that healthcare providers or lab techs use a concentration procedure to increase the chances the eggs will be seen.

Treatment

Multiple treatment options are available for hookworm, including some that can treat the infection in just one dose. Because these treatment options are safe and effective, they are often given preventively to individuals without a diagnosis or delivered to whole communities on an annual basis to keep infections under control.

With treatment, you can get rid of hookworms. You can expect a full recovery if you're treated before any serious complications develop.

Medications

Hookworm can be treated easily with a number of anthelminthic medications—like albendazole, mebendazole, and pyrantel pamoate—designed to rid the body of the parasites.

These drugs are taken by mouth over the course of one or three days, depending on the type of medication and its dose. They can be given to kids as young as 1 year old.

Iron Supplements

For kids, pregnant women, or others who develop anemia as a result of hookworm infection, healthcare providers will often prescribe an iron supplement in addition to an anti-worm medication.

These supplements help restore the body's iron stores. These are essential to making the red blood cells that carry oxygen throughout the body.

Preventive Chemotherapy

Hookworm treatment is sometimes given without a stool examination for groups at higher risk for hookworm in developing countries. This is called preventive treatment or preventive chemotherapy. The World Health Organization names the following as high-risk groups:

• Preschool and school-age children
• Women of childbearing age
• Adults who work in jobs with a high risk of infection

Mass Drug Administrations

Another tactic used to treat hookworm and other worms transmitted via contaminated soil is to give medications to whole communities presumptively. The drugs used to treat these infections are inexpensive, often donated, and safe with few side effects.

As a result, countries can slow or halt the spread of the worm in a given population by providing medication periodically, such as once a year. Healthcare providers, community health workers, or others visit households one by one to administer treatment for hookworm and other neglected tropical diseases.

Prevention

To prevent infection, keep the following tips in mind, especially in areas where hookworm is common:

• Wear shoes when you're outside.
• Avoid any skin contact with the soil, such as sitting on the ground.
• Don't ingest foods that have soil on them or water that may be contaminated.

Summary

People can get hookworm infections through soil contaminated with human feces. The hookworm larvae can burrow into your skin if you walk barefoot in the soil. You might also get it by ingesting food or water with soil in it.

A hookworm infection often doesn't cause any symptoms. If it does, it can cause symptoms like a localized rash, abdominal pain, diarrhea, lack of appetite, and weight loss. Over time, it can cause anemia and malnutrition.

Treatment is available to get rid of hookworms. Medications are taken by mouth for one to three days. For anemia, healthcare providers may prescribe an iron supplement.

A Word From Verywell

While no longer common in the United States, hookworm—along with other soil-transmitted helminths—continues to be a major cause of illness worldwide, especially among those with poor access to sanitation and effective treatment.

It's relatively uncommon for travelers to areas with hookworm to become infected, so long as they wear shoes while walking outside and thoroughly wash uncooked food. That said, if you have any symptoms of hookworm, see your healthcare provider right away to be tested for the worm and, if necessary, get treatment.