In the United States, the best-known skin-piercing parasitic worm, called a nematode, is the hookworm. But globally, it is estimated that more than 600 million people are infected with skin-penetrating threadworms, also known as Strongyloides stercoralis. This species is found mostly in tropical and subtropical regions with poor sanitation infrastructure. Nematodes that penetrate the skin are excreted in the feces of an infected host, and then enter the ground to wait for a new host. When they infect a new host, they can cause serious diseases.
