Question
Cyclops
Answer
Cyclops is a genus of small, free-living freshwater crustaceans (copepods), medically important as the obligate intermediate host for the guinea worm, Dracunculus medinensis — the causative agent of dracunculiasis (Guinea worm disease) — and also serves as an intermediate host for certain other parasites (e.g., some species of Diphyllobothrium, the fish tapeworm, use copepods as a first intermediate host).
Role in the Dracunculus medinensis life cycle: first-stage larvae released into fresh water (from the ruptured blister of an infected human, on contact with water) are ingested by Cyclops; within the copepod’s body cavity, the larvae develop over approximately 2 weeks into infective third-stage larvae — this developmental step within Cyclops is essential, since humans cannot become infected by the first-stage larvae directly, only by ingesting water containing Cyclops harbouring these mature infective larvae.
Human infection: occurs when a person drinks water from a source (typically a stagnant pond or step-well) containing infected Cyclops; the copepod is digested in the human stomach, releasing the infective larvae, which then penetrate the gut wall and begin their approximately year-long migration through human tissue to eventually emerge as the adult female worm at a distal body site (classically the lower leg), completing the cycle when the emerging worm’s blister again contacts water.
Public health/control significance: because Cyclops is an obligate intermediate host required for the parasite’s development, water source control measures targeting the removal or exclusion of Cyclops are central to Guinea worm eradication efforts — including filtration of drinking water through fine cloth/nylon mesh filters (which physically removes the copepods), use of protected/covered water sources, and larvicidal treatment (e.g., temephos) of contaminated ponds — these vector-control measures, combined with case containment (preventing infected individuals from re-entering water sources) and health education, have driven dracunculiasis to the brink of global eradication.