The infection is caused by infestation with any of the following roundworms:
The first 2 roundworms affect humans only. The last 2 types also occur in animals.
Hookworm disease is common in the moist tropics and subtropics. In developing nations, the disease leads to the death of many children by increasing their risk for infections that their bodies would normally fight off.
There is very little risk of getting the disease in the United States because of advances in sanitation and waste control. The important factor in getting the disease is walking barefoot on ground where there are feces of people who have hookworm.
The larvae (immature form of the worm) enter the skin. The larvae move to the lungs via the bloodstream and enter the airways. The worms are about one half inch long.
After traveling up the windpipe, the larvae are swallowed. After the larvae are swallowed, they infect the small intestine. They develop into adult worms and live there for 1 or more years. The worms attach to the intestinal wall and suck blood, which results in iron deficiency anemia and protein loss. Adult worms and larvae are released in the feces.
Hotez PJ. Hookworms (Necator americanus and Angylostoma spp.). In: Kliegman RM, Stanton BF, St. Geme, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 292.
Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.