It lives in the small intestine especially the jejunum[citation needed] of definitive hosts, generally humans,[2]: 307–308 [3] where it is able to mate and mature.

[4] Ancylostoma duodenale is abundant throughout the world, including Southern Europe, North Africa, India, China, Southeast Asia, some areas in the United States, the Caribbean, and South America.

It is then carried to the lungs, breaks into alveoli, ascends the bronchi and trachea, and is coughed up and swallowed back into the small intestine, where it matures.

The larva later matures into an adult in the small intestine (jejunum mainly[citation needed]), where they attach to the villi and female worms can lay 25,000 eggs per day.

These infective filariform larvae are able to sense vibrations in the soil, heat, or carbon dioxide, and employ dendritic processes similar to cilia.

A. duodenale is prevalent in Southern Europe, North Africa, India, China, Southeast Asia, small areas of United States, the Caribbean islands, and South America.

The way it enters the human body was understood in the 1880s, after an epidemic of ancylostomiasis among miners working in the hot and humid Gotthard Tunnel (Switzerland).

In pregnant women, this parasite is able to infect the fetus and can cause complications such as low birth weight, maternal anemia, and infant mortality.