The fox tapeworm (echinococcus multilocularis) belongs to the phylum of flatworms (platyhelminthes) and there to the class of tapeworms (cestoda). Like other tapeworms, it`s an endoparasite living in the intestine of its host and neither has a mouth nor an intestine, but absorbs its food through the skin. It consists of a head, with which it attaches itself to the intestinal wall of the fox, and a chain of four or five homogenous links (proglottids). The last link is continually loaded with mature eggs, constricted, and excreted togeher with the feces. Fox tapeworms only measure about 1,53cm. A single fox can host up to 200000 of these parasites without being visibly sick. With his feces, the fox also excretes tapeworm eggs. Thus they end up on the forest soil and on wild berries and mushrooms, and is finally ingested by mouses with their fod. In the mouses liver, the eggs develop into Finn (the larvae of the tapeworm). The eggs can also develop into larvae in the human liver. Because the liver tissue isn`t sensitive to pain, the disease is usually not immediately recognized. Just after five to fifteen year, when the majority of the liver is destroyed, diffuse pains in the upper abdomen indicate the disease (alveolar echinococcosis). Its therapy is very difficult and not always successful, only if it`s recognized in an early stage, healing can be attained by removing the affected areas of the liver. Later that that, a medical treatment can onyl stop the growth of the larvae. Due to this reason, in 1990 the World Health Organization (WHO) has classified the alveolar echinococcosis as the most dangerous parasitosis of central europe.