Diphyllobothrium latum is a flatworm which is considered to be one of the most dangerous human parasites. It may also infect dogs, cats, foxes, bears and other fish-eating animals. Diphyllobothrium latum infections are mainly found in Europe and North America. Infection with D. latum causes in humans the disease called diphyllobothriasis. The main definitive host of the tapeworm is human individual, who becomes infected by eating undercooked fish meat. The adult tapeworm is located in the human small intestine and along with the faeces, the eggs of the parasite get into the aquatic environment, where their further development takes place. The first intermediate host of D. latum is crustacean such as a copepod. Following ingestion of the copepod by a suitable second intermediate host, typically a minnow or other small freshwater fish, the parasite penetrates host’s intestinal wall and settles in the liver, spleen or reproductive glands of the fish.