Refers to parasitic nematodes of the family Ancylostomatidae, especially species that infect humans through the skin.
Hookworms are parasites that enter the body through the skin.
Hookworm infection can cause anemia.
From 鉤 (hook) + 虫 (worm, insect). The kanji 鉤 is less common in everyday use but is standard in this biological term.