Echinococcus multilocularis and alveolar hydatid in people

For E. multilocularis, as for E. granulosus, people are in the intermediate host position in the life cycle. If people ingest viable E. multilocularis eggs from carnivore feces, they can develop multilocular (alveolar) hydatid cysts, primarily in the liver. These cysts may be associated with clinical signs, but sometimes not until decades after infection. In North America, almost all of the locally acquired cases of alveolar hydatid in people have been in Alaska. The condition is extremely rare in people in Canada. That said, the geographic distribution of E. multilocularis in North America seems to be expanding southwards and eastwards, so that in areas of Alaska, the far north of Canada, and now much of the centre of the continent, including the prairie provinces, the parasite is considered endemic. Data from experimental infections suggest that domestic cats may not be a very suitable host for E. multilocularis, with poor parasite establishment and egg production.

Recently a dog with larval E. multilocularis (alveolar hydatid) in its liver was detected in northern British Columbia.  This is the first record of the parasite in the province.  The dog had traveled only locally, and the source of infection, the occurrence of the parasite in other possible local hosts, and the public health significance of this parasite in British Columbia are unknown.  Larval infections with E. multilocularis in dogs have been reported previously, particularly from the endemic areas of Europe, but the dog is usually the definitive host with adult parasites in the small intestine and eggs in the faeces.

Additional information about Echinococcus multilocularis is available under Dogs.