the broad tapeworm, is an intestinal parasite with a complex life cycle (humans, freshwater crustaceans and fishes and then again humans are infected in this order). The worm can be up to 12 meters long and it can survive for 10 years or more in the human intestine. This infection was common in the northern Europe, including Finland, but it is now rare. This worm has a great affinity for vitamin B12, sometimes causing deficiency in the human host, very seldom however anaemia.