Hookworms are tiny roundworms whose larvae can bore into the human skin. There are two types of hookworm that affect people, one type in the Eastern hemisphere (Ankylostoma duodenale causing ankylostomiasis) and the other in the Western hemisphere (Necator americanus causing uncinariasis). Both are acquired by direct skin penetration (usually of bare feet) from larvae in soil contaminated by human faeces. The larvae travel through the body to the lungs, then up towards the mouth and down into the upper intestine where they mature and can live by sucking blood. In a high intensity infection there are 80 or more worms passed in their faeces each time a person goes to toilet. Chronic infection is a major cause of shortage of blood (anaemia) because the adult worms live by sucking blood from inside the intestine. The blood shortage can sometimes be severe enough to cause heart failure. In infants development of mental and motor skills can be delayed. There is an effective drug treatment. The spread of infection and recurrence of infection can be reduced by good sanitation and wearing shoes.
Hookworm disease caused 0.005% of all deaths worldwide in 2002, with an average of 0.5 deaths per million people.