Hookworms that infect humans include the Ancylostoma duodenale and Necator americanus species.
These soil-transmitted worms are found in tropical and subtropical locations and thrive in moist, hot climates. However, hookworms can be found in many countries and continents including the United States, Africa, Asia, the Americas, the Middle East, Australia, and southern Europe.
According to the Centers for Disease Control and Prevention (CDC), between 576 and 740 million people worldwide have hookworm infections.
Hookworms tend to live in tropical and subtropical locations and do best in moist, hot climates.
The larvae of hookworm are transmitted through the skin after contamination with human feces. This often occurs by walking barefoot on soil or ingesting soil particles that have been contaminated with larvae.
Contamination can occur when a hookworm-infected person defecates in the soil or when human feces are used as fertilizer.
After ingestion or skin penetration, the hookworm larvae make their way into the body's bloodstream and lymphatic vessels. They are transported to the lungs and eventually the mouth.
Once digested, mature hookworms attach to the small intestine and gain nutrients through human blood. In some cases, this may lead to anemia from the loss of blood to the hookworms.
The small intestine is also the location where mating occurs, and thousands of eggs can be released into human feces. Despite the presence of hookworm in the feces, personal contact is not a method of transmission. The eggs need to mature into larvae within the soil.
There are certain groups of people who are at a higher risk of contracting the parasite. These groups include:
- People who live in warm, tropical, or subtropical areas
- People exposed to poor sanitation management and hygiene, especially if walking barefoot or with skin-to-soil contact
- Women who are pregnant and those who are of childbearing age
- Young children who are exposed to contaminated soil or sandboxes
- People who have contact with contaminated soil, especially farmers, plumbers, electricians, and exterminators
- People who sunbathe on contaminated sand
Other occupations with a higher risk include those that require crawling underneath raised buildings. The risk increases when "night soil" or fertilizer made from human feces is used.
People infected with hookworm may show some of the following symptoms:
Stomach pain and diarrhea are a couple of symptoms of a hookworm infection.
- Skin rash in one area that is typically red, raised, and itchy
- Weight loss
- Loss of appetite
- Breathing complications such as wheezing and cough
- Stomach pain
- 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 secondary to severe anemia
Diagnosis and treatment
To diagnose hookworm and its effects, healthcare providers may request certain testing including:
- A stool sample to check for hookworm eggs
- Blood samples to check for the presence of anemia or a lack of certain nutrients
Certain medications are recommended to treat a hookworm infection, usually given for 1 to 3 days. Medications such as albendazole or mebendazole may be given to treat the parasitic infection, and iron supplementation may be required for those with secondary anemia.
The drugs listed above have pregnancy warnings. People should disclose their pregnancy status to healthcare providers so that the right treatment options can be discussed.
The CDC report that, at times, preventive treatment for certain high-risk groups is necessary. These groups can include:
- People who live in developing countries with a higher than average risk for contracting hookworm
- Preschool and school children
- Childbearing-aged women
- Pregnant women in their second and third trimesters
- Lactating women
- People with high-risk jobs
There are certain preventive measures to avoid contracting a hookworm infection, including:
- 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 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 like wearing gloves and shoes when gardening
- Covering moist soil requiring frequent contact with a waterproof liner
- Treating pet dogs and cats for hookworm
Hookworms and pets
The animal strain of hookworm can spread to humans.
Hookworms can be present in household pets, including dogs and cats. The animal strain can be spread to humans in some cases.
The Companion Animal Parasite Council (CAPC) recommend fecal testing in cats and dogs, with more frequent testing in the kitten and puppy age groups.
Recommended testing includes a minimum of 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 can be taken to reduce hookworm transmission include:
- Following leash laws
- Keeping dogs under control
For additional information on cat and dog hookworm infections, visit the CAPC's website.
People who think that they may be at risk for contracting hookworm or are experiencing symptoms of infection should speak with their doctor. For recommendations on hookworm screening and treatment of a dog or cat, people should speak to a veterinarian.