Hookworm disease is an illness caused by one of two types of S-shaped worms that infect the intestine of humans (the worm's host): Necator americanus and Ancylostoma duodenale. The two species cause illness by attaching themselves to the lining of the small intestine and sucking a person's blood.

Both types of hookworm are similar. The adult worm of both is about 10 mm long, pinkish-white in color, and curved into an S-shape or double hook. The females produce about 10,000-20,000 eggs per day. These eggs are passed out of the host's body in feces. The eggs enter the soil, where they incubate. After about 48 hours, the immature larval form hatches out of the eggs. These larvae take about six weeks to develop into the mature larval form that is capable of causing human infection. If exposed to human skin at this point (usually bare feet walking in...