Hookworm is a parasite that causes infection in people of all ages. It enters the body through the skin and can lead to a number of complications.

Hookworm is most likely to occur in a moist, hot climate. However, they occur in many locations around the world, including the United States.

According to the Centers for Disease Control and Prevention (CDC), between 576 and 740 million people worldwide have hookworm infections. It was once common in the southeastern parts of the U.S., but improvements in living conditions have reduced its occurrence.

However, wherever humans and animals live together, including pets, infection is possible.

There are different species of hookworm. The ones that infect humans include the Ancylostoma duodenale and Necator americanus.

Hookworm can spread when a person who has the infection defecates in the soil or when people use human feces on soil as a fertilizer.

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Hookworms can enter the skin when a person comes into contact with contaminated soil.

If eggs are present in the feces, they can hatch after 1 to 2 days under the right conditions.

After hatching, the larvae can survive for 3 to 4 weeks in the soil, according to the Merck Manuals. They take 5 to 10 days to mature in the soil.

When a person comes into contact with this soil, hookworm larvae can pass through their skin.

This can happen if the person:

  • walks barefoot on soil that contains the larvae
  • swallows soil particles, for example on unwashed salad leaves

After entering the body, the hookworm larvae make their way into the body's bloodstream and lymphatic vessels. These systems carry the larvae to the lungs. From there, the person can cough them up and swallow them.

If a person digests mature hookworms, the worms attach to the small intestine and gain nutrients through human blood. In some cases, the person may develop anemia as they lose blood to the hookworms. Worms may live for over 2 years.

Mating also occurs in the small intestine. From here, thousands of eggs can enter the human feces.

Hookworms cannot pass to another individual through personal contact. Infection can only happen when the eggs mature into larvae in soil.

Certain groups of people have a higher risk of contracting the parasite.

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Walking barefoot on soil can expose a person to hookworm.

These include:

  • those who live in warm, tropical, or subtropical areas
  • people who spend time in areas where there is poor sanitation management and hygiene, especially if walking barefoot or with skin-to-soil contact
  • those who are pregnant or of childbearing age
  • young children who have contact with contaminated soil or sandboxes
  • workers who have contact with contaminated soil, especially farmers, plumbers, electricians, and exterminators
  • people who sunbathe on contaminated sand

The risk increases in areas where people use "night soil" or fertilizer made from human feces.

People with a hookworm infection may show some of the following symptoms:

  • a skin rash in one area that is typically red, raised, and itchy
  • weight loss
  • loss of appetite
  • breathing complications, such as wheezing and a cough
  • fever
  • stomach pain
  • diarrhea
  • extreme tiredness and weakness
  • iron deficiency anemia or malnutrition
  • physical and thought development problems in children due to severe anemia
  • heart failure and widespread tissue swelling as a result of severe anemia

A number of tests can help diagnose a hookworm infection and its effects.

These include:

  • a stool sample to check for hookworm eggs
  • blood samples to check for the presence of anemia or a lack of certain nutrients

A doctor will normally recommend taking certain medications — albendazole, mebendazole, or pyrantel pamoate — for 1 to 3 days to treat the parasitic infection, according to the CDC. These drugs are antihelminthics, or anti-parasitic drugs.

Those with severe anemia may need iron supplementation.

The drugs listed above have pregnancy warnings. People should tell their healthcare provider if they are or may be pregnant so that they can have the right treatment.

In places where hookworm is common, those who are at risk may receive preventive drug treatment to protect them from an infection.

Some preventive measures can help a person avoid contracting a hookworm infection.

These include:

  • wearing shoes, especially in soiled areas with a high risk of contamination
  • using a barrier to prevent the skin from touching the soil when sitting on the ground
  • avoiding consuming soil or unwashed foods that may be contaminated with hookworm
  • not passing stool in the soil or outdoors
  • not using fertilizer made from human feces
  • covering children's sandboxes
  • taking safety precautions, such as wearing gloves and shoes when gardening
  • treating pet dogs and cats for hookworm

The risk of hookworm is low in the U.S., but people should take care when travelling to holiday destinations where it is common.

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Taking pets to the vet regularly for testing and treatment can reduce the risk of catching and spreading hookworms.

Hookworms can be present in household pets, including dogs and cats. The animal strain can spread to humans in some cases.

For this reason, the Companion Animal Parasite Council (CAPC) recommend fecal testing in cats and dogs, with more frequent testing in the kitten and puppy age groups.

The CAPC recommend at least four intestinal parasite tests in the first year and a minimum of two a year afterward. As with any preventive testing, the animals' health and certain risk factors will guide how often testing is needed.

To prevent parasitic infection, the CAPC recommend year-round broad-spectrum parasite control and also recommend promptly removing animal stool from litter boxes and yards.

Other public safety measures that people can take to reduce hookworm transmission include:

  • following leash laws when in public
  • preventing dogs from wandering neighborhoods or scavenging
  • following a vet's advice about deworming

For additional information on cat and dog hookworm infections, visit the CAPC's website.

People should speak to a doctor if they:

  • think they may be at risk for contracting hookworm
  • are experiencing symptoms of infection after travelling or coming into contact with soil used by pets

A veterinarian can offer advice on screening and treatment of a dog or cat.

Q:

I live in Illinois and I have pets. Do I need to worry about hookworm?

A:

Unfortunately, yes.

According to the Illinois state website, hookworm may be present statewide in Illinois.

This is due, in large part, to the moist, hot climate found in many of the woodland, aquatic, and prairie regions in Illinois. However, hookworms can be present wherever people and animals live.

Following some of the habits mentioned above will help avoid ever having to deal with them.

These include avoiding contact with human stool, washing produce, and working with your veterinarian to determine the best parasite prevention plan for your pets.

Vincent J. Tavella, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.