Echinococcus multilocularis and Alveolar Echinococcosis: Should We Be Concerned?

Alveolar echinococcosis (AE) is a life-threatening zoonotic infection caused by Echinococcus multilocularis, an intestinal cestode of carnivorous animals (mostly canids). Its life cycle includes an adult stage in the intestines of carnivores and a larval stage (metacestode) in tissues of herbivores or omnivores. Humans are accidental/aberrant hosts and harbor the metacestode only. The disease presents as a continuously growing tumor-like liver mass with local or metastatic spread to distant organs, with mortality approaching 90% if untreated or partially treated. Diagnosis is based on characteristic imaging, serology and histopathology, and confirmation by nucleic acid amplification test. The geographical distribution of E. multilocularis covers most of the northern hemisphere, with human cases in Europe, Japan, Central Asia, and now North America. The recent establishment of a new parasite strain that is pathogenic to humans in Canada and the United States poses an emerging medical and public health threat and warrants a reassessment of our approach to this parasite.