Echinococcus multilocularis in an imported captive European beaver (Castor fiber) in Great Britain

Echinococcus multilocularis (tapeworm) is one of the most pathogenic parasitic zoonoses in central Europe. The definitive (final) wildlife hosts in Europe are canid carnivores, predominantly the red fox ( Vulpes vulpes ) and now the non-native raccoon dog ( Nyctereutes procyonoides ). The domestic dog and cat are also definitive hosts. While the dog exhibits susceptibility to infection similar to that of foxes, tapeworms in cats rarely reach maturity, thus cats seem not to play a significant role in the transmission cycle. Adult tapeworms live in the small intestines of the definitive hosts and parasite proglottids and eggs are shed in the faeces. Intermediate hosts are infected when they ingest eggs, which then, upon release of an oncosphere, develop into larvae (metacestode stage with finally protoscolices) that form vesiculated small cysts in internal organs, mainly the liver and lungs but also brain. These parasite vesicles proliferate continuously and lead to a cancer-like disease in affected intermediate hosts. The sylvatic cycle is completed by carnivore predation of such infected intermediate hosts. Several species of small mammals, mainly microtine or arvicolid rodents, are the main intermediate hosts (Eckert and others 2001), as well as two newly introduced species, the coypu ( Myocastor coypus ) and the muskrat ( Ondatra zibethicus ) (Mathy and others 2009) among others. The raccoon dog, coypu and muskrat are not feral in Great Britain (GB). The European beaver (Castor fiber) is one of the further intermediate host and the …