Hookworm infection, also known as hookworm disease, is an infection by a parasitic bloodsucking roundworm. Hookworm infections include ancylostomiasis and necatoriasis. These worms live in the small intestine of their host, which may be a bird or a mammal such as a dog, cat, or human. Hookworm infection in pregnancy can cause retarded growth of the fetus, premature birth and a low birth weight. Hookworms in children can cause intellectual, cognitive and growth problems.