Echinococcus multilocularis in New York Wildlife: Distribution and Genetic Diversity of an Emerging Pathogen

Echinococcus is a genus of cestode parasites of paramount veterinary and medical importance globally. Two species, Echinococcus granulosus sensu lato and Echinococcus multilocularis, are endemic to North America and are the etiologic agents of cystic echinococcosis and alveolar echinococcosis, respectively. North America is currently experiencing an epidemiological shift in the state of transmission, distribution, and prevalence of E. multilocularis, following the introduction of the European variant of the parasite. The rapid expansion of the parasite into the northeastern United States has resulted in novel detections of spillover to humans, indicating the need for active surveillance to direct public health education and disease control measures. Our surveillance of the parasite in definitive hosts in New York State from 2019 to 2023 yielded 8 detections of the parasite, for a sample prevalence of 8.3% (8/96). Phylogenetic analysis of mitochondrial markers confirmed that all New York isolates belong to the European lineage and group in a well-supported clade with E. multilocularis isolates described from Slovakia and Poland. Investigation of the highly polymorphic EmsB microsatellite marker revealed several E. multilocularis genotypes circulating in New York, including 1 that is distinct from European isolates detected in western North America. These data are consistent with 1 or more unique introductions from Europe rather than a spread from western regions of Canada and the United States, where other European variants are found. Echinococcus multilocularis appears to have a complex epidemiology in North America that warrants further detailed surveillance to evaluate the risks for zoonotic transmission.