A threadlike worm 30 to 120 cm long that inhabits the subcutaneous and intermuscular tissues of humans and domestic animals in India, Africa, and the Arabian peninsula, causing dracunculiasis.

Its embryos are discharged through an opening in the skin upon contact with water; from the water they enter the body of a small crustacean, Cyclops, where they undergo larval development. Also known as: dragon worm, guinea worm, Medina worm, and serpent worm.