A hookworm is any type of roundworm. This parasite causes intestinal infection in animals and humans. It is very common. In fact, about one-fourth of the world's population is infected with hookworms.

What is going on in the body?

Hookworm eggs need warm, moist soil in order to develop into larvae. Humans can acquire the parasite by coming in contact with contaminated soil, often by walking with bare feet. The worms penetrate the skin, enter the bloodstream, and are carried to the lungs. From there, they travel up the airway to the mouth, are swallowed, and sent to the small intestine.

Once in the small intestine, the worms attach themselves to the intestinal wall. It is there that the females will lay their eggs into the fecal stream. These eggs, if passed into the soil, will begin the life cycle again.

What are the causes and risks of the infection?

Hookworm is most common in warm, moist places where sanitation is poor. Transmission usually occurs through contaminated soil. It is due either to a lack of sanitary facilities or to the use of human manure as fertilizer. Infection can occur when foods contaminated with hookworm cysts are eaten.