Fluke

Fluke is a term with several distinct meanings in science, biology, and everyday language. In biology and parasitology, it refers to a group of flatworms known as flukes (class Trematoda). In anatomy and nautical contexts, it describes a part of an animal or a piece of equipment, and in everyday speech it can mean a lucky accident or chance occurrence.

Parasitic flukes are obligate parasites with complex life cycles often requiring a snail as an intermediate host and a vertebrate as the final host. They inhabit organs such as the liver, lungs, or intestines of their hosts. Notable species include Fasciola hepatica (the common liver fluke) and Fasciola gigantica, which cause fascioliasis in livestock and sometimes humans; Clonorchis sinensis (the Chinese liver fluke); and Paragonimus westermani (the lung fluke). Transmission commonly involves contaminated water, ingestion of aquatic intermediate hosts, or undercooked seafood. Clinically, fluke infections can cause abdominal pain, bile duct obstruction, coughing, or other organ-specific symptoms. Diagnosis relies on finding parasite eggs or DNA in stool or sputum, and treatment typically involves antiparasitic drugs such as praziquantel. Control emphasizes sanitation, snail control, and proper cooking of intermediate hosts.

In cetaceans, the fluke is the broad, horizontal tail fin used for propulsion. In nautical terminology, flukes are the blades of an anchor that dig into the seabed to hold a vessel in place. The word also appears in the idiom by a fluke, meaning a chance or lucky occurrence, reflecting an informal sense of luck rather than a biological one.